Network Working Group                               B. Desruisseaux, Ed.
Internet-Draft                                                    Oracle
Obsoletes: 2445 (if approved)                              June 22, 2006
Expires: April 14, December 24, 2006                                   C. Stoner, Ed.
                                                                     IBM
                                                        October 11, 2005

     Internet Calendaring and Scheduling Core Object Specification
                              (iCalendar)
                    draft-ietf-calsify-rfc2445bis-00
                    draft-ietf-calsify-rfc2445bis-01

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Copyright Notice

   Copyright (C) The Internet Society (2005). (2006).

Abstract

   Calendar systems export, transport and sometimes even store calendar
   information in

   There is a standard, clear need to provide and deploy interoperable format. calendaring
   and scheduling services for the Internet.  Current group scheduling
   and Personal Information Management (PIM) products are being extended
   for use across the Internet, today, in proprietary ways.  This memo defines
   has been defined to provide the definition of a common format for
   openly exchanging calendaring and scheduling information across the Internet,
   Internet.

   This memo is formatted as a registration for a MIME media type .
   However, the format in this memo is equally applicable for use
   outside of a MIME message content type.

   The proposed media type value is 'text/calendar'.  This string would
   label a media type containing calendaring and scheduling information
   encoded as text characters formatted in a manner outlined below.

   This MIME media type provides a standard content type for capturing
   calendar event, to-do and journal entry information.  It also can be
   used to convey free/busy time information.  The content type is
   suitable as a MIME message entity that can be transferred over MIME
   based email systems, using HTTP or some other Internet transport.  In
   addition, the content type is useful as an object for interactions
   between desktop applications using the operating system clipboard,
   drag/drop or file systems capabilities.

   This memo is based on the earlier work of the vCalendar specification
   for the exchange of personal calendaring and scheduling information.
   In order to avoid confusion with this referenced work, this memo is
   to be known as the iCalendar specification.

   This memo defines the format for specifying iCalendar object
   format. methods.
   An iCalendar object may represent method is a set of usage constraints for the
   iCalendar object.  For example, these methods might define scheduling
   messages that request an event be scheduled, reply to an event
   request, send a cancellation notice for an event, to-do modify or replace
   the definition of an event, provide a counter proposal for an
   original event request, delegate an event request to another
   individual, request free or busy time, reply to a free or busy time
   request, or task, provide similar scheduling messages for a to-do or
   journal entry (note). calendar component.  The iCalendar Transport-indendent
   Interoperability Protocol (iTIP) is one such scheduling protocol.

Editorial Note

   This document is a product of the Calendaring and Scheduling
   Standards Simplification (Calsify) working group of the Internet
   Engineering Task Force.  Comments on this draft are solicited welcomed, and
   should be addressed to the working group's ietf-calsify@osafoundation.org [1] mailing
   list.

   A detailed list of changes is available at ietf-calsify@osafoundation.org and/or the editor. following page:
   http://www.geocities.com/bdesruisseaux/calsify/
   draft-ietf-calsify-rfc2445bis-01.html.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   5
     1.1.   Related Memos  . . .   6
   2.  Basic Grammar and Conventions . . . . . . . . . . . . . . . .   6
     2.1.  Formatting Conventions  . .   5
   2.  Overview . . . . . . . . . . . . . . .   7
     2.2.  Related Memos . . . . . . . . . . .   7
   3.  Document Conventions . . . . . . . . . . .   8
     2.3.  International Considerations  . . . . . . . . .   8
     3.1.   Formatting Conventions . . . . .   8
   3.  iCalendar Object Specification  . . . . . . . . . . . .   8
   4.  International Considerations . . .   9
     3.1.  Content Lines . . . . . . . . . . . . .  10
   5.  General Syntax . . . . . . . . .   9
       3.1.1.  List and Field Separators . . . . . . . . . . . . . .  11
     5.1.   Character Set  . . . .
       3.1.2.  Multiple Values . . . . . . . . . . . . . . . . .  11
     5.2.   Case Sensitivity . .  12
       3.1.3.  Binary Content  . . . . . . . . . . . . . . . . . .  11
     5.3.   Content Lines .  12
       3.1.4.  Character Set . . . . . . . . . . . . . . . . . . . .  11
     5.4.   List and Field Separators  13
     3.2.  Property Parameters . . . . . . . . . . . . . . .  14
     5.5.   Multiple Property Values . . . .  13
       3.2.1.  Alternate Text Representation . . . . . . . . . . . .  14
     5.6.   Binary Content
       3.2.2.  Common Name . . . . . . . . . . . . . . . . . . . . .  15
     5.7.   Property Parameter Syntax
       3.2.3.  Calendar User Type  . . . . . . . . . . . . . . .  15
   6.  iCalendar Objects . .  16
       3.2.4.  Delegators  . . . . . . . . . . . . . . . . . . . .  17
   7.  Calendar Components .  16
       3.2.5.  Delegatees  . . . . . . . . . . . . . . . . . . . .  18
     7.1.   Event Component .  17
       3.2.6.  Directory Entry Reference . . . . . . . . . . . . . .  17
       3.2.7.  Inline Encoding . . . . .  19
     7.2.   To-do Component . . . . . . . . . . . . . .  18
       3.2.8.  Format Type . . . . . .  22
     7.3.   Journal Component . . . . . . . . . . . . . . .  19
       3.2.9.  Free/Busy Time Type . . . .  24
     7.4.   Free/Busy Component . . . . . . . . . . . . .  19
       3.2.10. Language  . . . . .  26
     7.5.   Time Zone Component . . . . . . . . . . . . . . . . .  20
       3.2.11. Group or List Membership  .  29
     7.6.   Alarm Component . . . . . . . . . . . . .  21
       3.2.12. Participation Status  . . . . . . .  38
   8.  Properties . . . . . . . . .  21
       3.2.13. Recurrence Identifier Range . . . . . . . . . . . . .  23
       3.2.14. Alarm Trigger Relationship  . . .  45
     8.1.   Calendar Properties . . . . . . . . . .  23
       3.2.15. Relationship Type . . . . . . . .  45
       8.1.1.  Calendar Scale . . . . . . . . . .  24
       3.2.16. Participation Role  . . . . . . . . .  45
       8.1.2.  Method . . . . . . . .  25
       3.2.17. RSVP Expectation  . . . . . . . . . . . . . . .  46
       8.1.3.  Product Identifier . . .  25
       3.2.18. Sent By . . . . . . . . . . . . . . .  47
       8.1.4.  Version . . . . . . . .  26
       3.2.19. Time Zone Identifier  . . . . . . . . . . . . . . .  48
     8.2.   Descriptive Component Properties .  26
       3.2.20. Value Data Types  . . . . . . . . . . .  49
       8.2.1.  Attachment . . . . . . .  28
     3.3.  Property Value Data Types . . . . . . . . . . . . . .  49
       8.2.2.  Categories . .  29
       3.3.1.  Binary  . . . . . . . . . . . . . . . . . . .  50
       8.2.3.  Classification . . . .  29
       3.3.2.  Boolean . . . . . . . . . . . . . . .  51
       8.2.4.  Comment . . . . . . . .  30
       3.3.3.  Calendar User Address . . . . . . . . . . . . . . .  52
       8.2.5.  Description .  30
       3.3.4.  Date  . . . . . . . . . . . . . . . . . . . .  53
       8.2.6.  Geographic Position . . . .  31
       3.3.5.  Date-Time . . . . . . . . . . . . .  54
       8.2.7.  Location . . . . . . . . .  31
       3.3.6.  Duration  . . . . . . . . . . . . .  56
       8.2.8.  Percent Complete . . . . . . . . .  34
       3.3.7.  Float . . . . . . . . .  57
       8.2.9.  Priority . . . . . . . . . . . . . . .  34
       3.3.8.  Integer . . . . . . .  58
       8.2.10. Resources . . . . . . . . . . . . . . . .  35
       3.3.9.  Period of Time  . . . . . .  59
       8.2.11. Free/Busy Time Type . . . . . . . . . . . . .  35
       3.3.10. Recurrence Rule . . . .  60
       8.2.12. Participation Status . . . . . . . . . . . . . . .  37
       3.3.11. Text  .  61
       8.2.13. Status . . . . . . . . . . . . . . . . . . . . . . .  63
       8.2.14. Summary  42
       3.3.12. Time  . . . . . . . . . . . . . . . . . . . . . . .  64
       8.2.15. Date and Time Component Properties .  43
       3.3.13. URI . . . . . . . .  65
       8.2.16. Time Zone Component Properties . . . . . . . . . . .  73
       8.2.17. Relationship Component Properties . . . . . .  46
       3.3.14. UTC Offset  . . . .  77
       8.2.18. Calendar User Type . . . . . . . . . . . . . . . . .  86
       8.2.19. Directory Entry Reference  46
     3.4.  iCalendar Object  . . . . . . . . . . . . . .  87
       8.2.20. Recurrence ID . . . . . .  47
     3.5.  Property  . . . . . . . . . . . . . .  87
       8.2.21. Related To . . . . . . . . . .  48
     3.6.  Calendar Components . . . . . . . . . . . .  89
       8.2.22. Uniform Resource Locator . . . . . . .  48
       3.6.1.  Event Component . . . . . . .  91
       8.2.23. Unique Identifier . . . . . . . . . . . .  49
       3.6.2.  To-do Component . . . . . .  91
       8.2.24. Relationship Type . . . . . . . . . . . . .  52
       3.6.3.  Journal Component . . . . .  93
     8.3.   Recurrence Component Properties . . . . . . . . . . . .  94
       8.3.1.  Exception Date/Times .  54
       3.6.4.  Free/Busy Component . . . . . . . . . . . . . . .  94
       8.3.2.  Exception Rule . .  55
       3.6.5.  Time Zone Component . . . . . . . . . . . . . . . . .  95
       8.3.3.  Recurrence Date/Times  58
       3.6.6.  Alarm Component . . . . . . . . . . . . . . . .  97
       8.3.4.  Recurrence Identifier Range . . .  66
     3.7.  Calendar Properties . . . . . . . . . .  98
       8.3.5.  Recurrence Rule . . . . . . . . .  72
       3.7.1.  Calendar Scale  . . . . . . . . . .  99
     8.4.   Alarm Component Properties . . . . . . . . .  72
       3.7.2.  Method  . . . . . . 110
       8.4.1.  Action . . . . . . . . . . . . . . . . .  73
       3.7.3.  Product Identifier  . . . . . . 110
       8.4.2.  Alarm Repeat Count . . . . . . . . . . .  74
       3.7.4.  Version . . . . . . 111
       8.4.3.  Alarm Trigger . . . . . . . . . . . . . . . . .  75
     3.8.  Component Properties  . . . 111
     8.5.   Alarm Trigger Relationship . . . . . . . . . . . . . . . 114
     8.6.   Change Management  76
       3.8.1.  Descriptive Component Properties  . . . . . . . . . 114
       8.6.1.  Date/Time Created .  76
         3.8.1.1.  Attachment  . . . . . . . . . . . . . . . . . 114
       8.6.2.  Date/Time Stamp . .  76
         3.8.1.2.  Categories  . . . . . . . . . . . . . . . . . 115
       8.6.3.  Last Modified . .  77
         3.8.1.3.  Classification  . . . . . . . . . . . . . . . . .  78
         3.8.1.4.  Comment . 116
       8.6.4.  Sequence Number . . . . . . . . . . . . . . . . . . . 117
     8.7.   Miscellaneous Component Properties .  79
         3.8.1.5.  Description . . . . . . . . . . 118
       8.7.1.  RSVP Expectation . . . . . . . . .  80
         3.8.1.6.  Geographic Position . . . . . . . . . 118
       8.7.2.  Language . . . . . .  81
         3.8.1.7.  Location  . . . . . . . . . . . . . . . . 119
       8.7.3.  Group or List Membership . . . .  83
         3.8.1.8.  Percent Complete  . . . . . . . . . . 120
       8.7.4.  Alternate Text Representation . . . . . .  84
         3.8.1.9.  Priority  . . . . . . 121
       8.7.5.  Inline Encoding . . . . . . . . . . . . . .  85
         3.8.1.10. Resources . . . . . 121
       8.7.6.  Format Type . . . . . . . . . . . . . . .  87
         3.8.1.11. Status  . . . . . . 122
       8.7.7.  Non-standard Properties . . . . . . . . . . . . . . . 123
       8.7.8.  Request Status  87
         3.8.1.12. Summary . . . . . . . . . . . . . . . . . . . 124
   9.  iCalendar Object Examples . .  89
       3.8.2.  Date and Time Component Properties  . . . . . . . . .  90
         3.8.2.1.  Date/Time Completed . . . . . . . 127
   10. Recommended Practices . . . . . . . .  90
         3.8.2.2.  Date/Time End . . . . . . . . . . . . 132
   11. Registration of Content Type Elements . . . . . .  91
         3.8.2.3.  Date/Time Due . . . . . . 134
     11.1.  Registration of New and Modified iCalendar Object
            Methods . . . . . . . . . . . .  92
         3.8.2.4.  Date/Time Start . . . . . . . . . . . . 134
     11.2.  Registration of New Properties . . . . .  93
         3.8.2.5.  Duration  . . . . . . . . 134
     11.3.  Define the property . . . . . . . . . . . .  94
         3.8.2.6.  Free/Busy Time  . . . . . . 134
     11.4.  Post the Property definition . . . . . . . . . . .  95
         3.8.2.7.  Time Transparency . . . 136
     11.5.  Allow a comment period . . . . . . . . . . . . .  96
       3.8.3.  Time Zone Component Properties  . . . . . . 136
     11.6.  Submit the property for approval . . . . .  97
         3.8.3.1.  Time Zone Identifier  . . . . . . . 136
     11.7.  Property Change Control . . . . . . .  98
         3.8.3.2.  Time Zone Name  . . . . . . . . . 136
   12. Property Parameters . . . . . . . .  99
         3.8.3.3.  Time Zone Offset From . . . . . . . . . . . . . 138
   13. Value Data Types . 100
         3.8.3.4.  Time Zone Offset To . . . . . . . . . . . . . . . 101
         3.8.3.5.  Time Zone URL . . . . . . 139
     13.1.  Binary . . . . . . . . . . . . 101
       3.8.4.  Relationship Component Properties . . . . . . . . . . 102
         3.8.4.1.  Attendee  . . . 139
     13.2.  Boolean . . . . . . . . . . . . . . . . . 102
         3.8.4.2.  Contact . . . . . . . 140
     13.3.  Calendar User Address . . . . . . . . . . . . . . 105
         3.8.4.3.  Organizer . . . 140
     13.4.  Date . . . . . . . . . . . . . . . . . 106
         3.8.4.4.  Recurrence ID . . . . . . . . . . 141
     13.5.  Date-Time . . . . . . . . 108
         3.8.4.5.  Related To  . . . . . . . . . . . . . . . 141
     13.6.  Duration . . . . 110
         3.8.4.6.  Uniform Resource Locator  . . . . . . . . . . . . 112
         3.8.4.7.  Unique Identifier . . . . . . . . 143
     13.7.  Period of Time . . . . . . . . 112
       3.8.5.  Recurrence Component Properties . . . . . . . . . . . 114
         3.8.5.1.  Exception Date/Times  . . 144
     13.8.  Time Zone Identifier . . . . . . . . . . . . 114
         3.8.5.2.  Exception Rule  . . . . . . 145
     13.9.  Recurrence Rule . . . . . . . . . . . 115
         3.8.5.3.  Recurrence Date/Times . . . . . . . . . . 146
     13.10. Float . . . . 117
         3.8.5.4.  Recurrence Rule . . . . . . . . . . . . . . . . . 118
       3.8.6.  Alarm Component Properties  . . . . . 152
     13.11. Integer . . . . . . . . 127
         3.8.6.1.  Action  . . . . . . . . . . . . . . . . 152
     13.12. Text . . . . . 128
         3.8.6.2.  Repeat Count  . . . . . . . . . . . . . . . . . . 128
         3.8.6.3.  Trigger . . . 153
     13.13. Time . . . . . . . . . . . . . . . . . . 129
       3.8.7.  Change Management Component Properties  . . . . . . . 131
         3.8.7.1.  Date/Time Created . 154
     13.14. URI . . . . . . . . . . . . . . . 132
         3.8.7.2.  Date/Time Stamp . . . . . . . . . . . 156
     13.15. UTC Offset . . . . . . 132
         3.8.7.3.  Last Modified . . . . . . . . . . . . . . . . . 157
   14. Security Considerations . 133
         3.8.7.4.  Sequence Number . . . . . . . . . . . . . . . . . 134
       3.8.8.  Miscellaneous Component Properties  . 159
   15. IANA MIME Media Type Registration . . . . . . . . 136
         3.8.8.1.  Non-standard Properties . . . . . . 160
   16. Acknowledgements . . . . . . . 136
         3.8.8.2.  Request Status  . . . . . . . . . . . . . . . 163
   17. Normative References . . 137
   4.  iCalendar Object Examples . . . . . . . . . . . . . . . . . . 163
   Authors' Addresses 140
   5.  Recommended Practices . . . . . . . . . . . . . . . . . . . . 144
   6.  Registration of Content Type Elements . . . 165
   Intellectual Property and Copyright Statements . . . . . . . . . 166

1.  Introduction

   The use 145
     6.1.  Registration of calendaring New and scheduling has grown considerably in Modified iCalendar Object
           Methods . . . . . . . . . . . . . . . . . . . . . . . . . 145
     6.2.  Registration of New Properties  . . . . . . . . . . . . . 145
       6.2.1.  Define the property . . . . . . . . . . . . . . . . . 146
       6.2.2.  Post the Property definition  . . . . . . . . . . . . 147
       6.2.3.  Allow a comment period  . . . . . . . . . . . . . . . 147
       6.2.4.  Submit the property for approval  . . . . . . . . . . 147
     6.3.  Property Change Control . . . . . . . . . . . . . . . . . 148
   7.  Internationalization Considerations . . . . . . . . . . . . . 148
   8.  Security Considerations . . . . . . . . . . . . . . . . . . . 148
   9.  IANA Consideration  . . . . . . . . . . . . . . . . . . . . . 149
     9.1.  Media Type Registration Information . . . . . . . . . . . 149
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 152
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . . 152
     11.1. Normative References  . . . . . . . . . . . . . . . . . . 152
     11.2. Informative References  . . . . . . . . . . . . . . . . . 153
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . 155
   Intellectual Property and Copyright Statements  . . . . . . . . . 156

1.  Introduction

   The use of calendaring and scheduling has grown considerably in the
   last decade.  Enterprise and inter-enterprise business has become
   dependent on rapid scheduling of events and actions using this
   information technology.  However, the longer term growth of
   calendaring and scheduling, is currently limited by the lack of
   Internet standards for the message content types that are central to
   these knowledgeware applications.  This memo is intended to progress
   the level of interoperability possible between dissimilar calendaring
   and scheduling applications.  This memo defines a MIME [5] content type
   for exchanging electronic calendaring and scheduling information.
   The Internet Calendaring and Scheduling Core Object Specification, or
   iCalendar, allows for the capture and exchange of information
   normally stored within a calendaring and scheduling application; such
   as a Personal Information Manager (PIM) or a Group Scheduling
   product.

   The iCalendar format is suitable as an exchange format between
   applications or systems.  The format is defined in terms of a MIME
   content type.  This will enable the object to be exchanged using
   several transports, including but not limited to SMTP, HTTP, a file
   system, desktop interactive protocols such as the use of a memory-
   based clipboard or drag/drop interactions, point-to-point
   asynchronous communication, wired-network transport, or some form of
   unwired transport such as infrared might also be used.

   The memo also provides for the definition of iCalendar object methods
   that will map this content type to a set of messages for supporting
   calendaring and scheduling operations such as requesting, replying
   to, modifying, and canceling meetings or appointments, to-dos and
   journal entries.  The iCalendar object methods can be used to define
   other calendaring and scheduling operations such a requesting for and
   replying with free/busy time data.  [[Comment.1: Removed forward
   reference to ITIP (unnecessary) --Lisa D]]  Such a scheduling protocol is
   defined in the iCalendar Transport-independent Interoperability
   Protocol (iTIP) defined in [I-D.ietf-calsify-2446bis].

   The memo also includes a formal grammar for the content type based on
   the Internet ABNF defined in RFC 2234 [8]. [RFC2234].  This ABNF is required for
   the implementation of parsers and to serve as the definitive
   reference when ambiguities or questions arise in interpreting the
   descriptive prose definition of the memo.

1.1.  Related Memos

   Implementers will need

2.  Basic Grammar and Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY" and
   "OPTIONAL" in this document are to be familiar with several other memos that,
   along with this memo, form interoperated as described in
   [RFC2119].

   This memo makes use of both a framework descriptive prose and a more formal
   notation for Internet defining the calendaring and scheduling standards.  This memo, [ICAL], specifies a core
   specification format.

   The notation used in this memo is the ABNF notation of objects, data types, properties and property
   parameters.

   [ITIP] - specifies an interoperability protocol for scheduling
   between different implementations;

   [IMIP] specifies an Internet email binding for [ITIP].

   This [RFC2234].
   Readers intending on implementing this format defined in this memo does not attempt
   should be familiar with this notation in order to repeat properly interpret
   the specification specifications of concepts or
   definitions from these other memos.  Where possible, references are
   made to the memo that provides for the specification of these
   concepts or definitions.  [[Comment.2: If we keep this section on
   related memos, we have to think about whether ITIP and IMIP are
   progressing to Draft at the same time, whether to update those
   references and whether to add CalDAV or other references. --Lisa D]]

2.  Overview

   This draft section provides a high-level overview of the concepts of
   iCalendar and the organization of memo.

   All numeric values used in this document.

   An iCalendar object contains a set of calendar properties and a set
   of components.  Components consist of a set of component properties.
   Properties consist memo are given in decimal notation.

   All names of a properties, property name, a set of parameters, and a enumerated property value.

   The preliminary material of this document includes the introduction,
   this overview, some document conventions and the considerations for
   internationalization.

   Section 5 provides the general syntax rules used by all of iCalendar,
   such as character set, line length and line break rules,
   values and which
   characters property parameter values are separators.

   Section 6 defines the iCalendar object itself, and Section 7 covers
   the components that appear in iCalendar objects.

3.  Document Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY" and
   "OPTIONAL" in this document case-insensitive.  However,
   all other property values are to be interoperated as described in
   RFC 2119 [7].

   This memo makes use of both a descriptive prose and a more formal
   notation for defining the calendaring and scheduling format.

   The notation used in this memo is the ABNF notation of RFC 2234 [8].
   Readers intending on implementing this format defined in this memo
   should be familiar with this notation in order to properly interpret
   the specifications of this memo. case-sensitive, unless otherwise
   stated.

      Note: All indented editorial notes, such as this one, are intended
      to provide the reader with additional information.  The
      information is not essential to the building of an implementation
      conformant with this memo.  The information is provided to
      highlight a particular feature or characteristic of the memo.  [[Comment.3: This section can
   be deleted because it provides practically no information and is not
   a normative reference:

   The format for the iCalendar object is based on the syntax of the RFC 2425
   [RFC2425] content type.  While the iCalendar object is not a profile
   of the RFC 2425 [RFC2425] content type, it does reuse a number of the elements
   from the RFC 2425 [RFC2425] specification. --Lisa D]]

3.1.

2.1.  Formatting Conventions

   The mechanisms defined in this memo are defined in prose.  Many of
   the terms used to describe these have common usage that is different
   than the standards usage of this memo.  In order to reference within
   this memo elements of the calendaring and scheduling model, core
   object (this memo) or interoperability protocol [ITIP] [I-D.ietf-calsify-
   2446bis] some formatting conventions have been used.  Calendaring and
   scheduling roles are referred to in quoted-strings of text with the
   first character of each word in upper case.  For example, "Organizer"
   refers to a role of a "Calendar User" within the scheduling protocol
   defined by [ITIP]. [I-D.ietf-calsify-2446bis].  Calendar components defined
   by this memo are referred to with capitalized, quoted-strings of
   text.  All calendar components start with the letter "V".  For
   example, "VEVENT" refers to the event calendar component, "VTODO"
   refers to the to-do calendar component and "VJOURNAL" refers to the
   daily journal calendar component.  Scheduling methods defined by [ITIP] iTIP
   [I-D.ietf-calsify-2446bis] are referred to with capitalized, quoted-strings quoted-
   strings of text.  For example, "REQUEST" refers to the method for
   requesting a scheduling calendar component be created or modified,
   "REPLY" refers to the method a recipient of a request uses to update
   their status with the "Organizer" of the calendar component.

   The properties defined by this memo are referred to with capitalized,
   quoted-strings of text, followed by the word "property".  For
   example, "ATTENDEE" property refers to the iCalendar property used to
   convey the calendar address of a calendar user.  Property parameters
   defined by this memo are referred to with lowercase, quoted-strings
   of text, followed by the word "parameter".  For example, "value"
   parameter refers to the iCalendar property parameter used to override
   the default data type for a property value.  Enumerated values
   defined by this memo are referred to with capitalized text, either
   alone or followed by the word "value".  For example, the "MINUTELY"
   value can be used with the "FREQ" component of the "RECUR" data type
   to specify repeating components based on an interval of one minute or
   more.

4.

2.2.  Related Memos

   Implementers will need to be familiar with several other memos that,
   along with this memo, form a framework for Internet calendaring and
   scheduling standards.  This memo specifies a core specification of
   objects, data types, properties and property parameters.

   o  iTIP [I-D.ietf-calsify-2446bis] specifies an interoperability
      protocol for scheduling between different implementations;

   o  iMIP [I-D.ietf-calsify-rfc2447bis] specifies an Internet email
      binding for [I-D.ietf-calsify-2446bis].

   This memo does not attempt to repeat the specification of concepts or
   definitions from these other memos.  Where possible, references are
   made to the memo that provides for the specification of these
   concepts or definitions.

2.3.  International Considerations

   In the rest of this document, descriptions of characters are of the
   form "character name (codepoint)", where "codepoint" is from the US-
   ASCII character set.  The "character name" is the authoritative
   description; (codepoint) is a reference to that character in US-ASCII
   or US-ASCII compatible sets (for example the ISO-8859-x family, UTF-
   8, ISO-2022-xx, KOI8-R).  If a non-US-ASCII compatible character set
   is used, appropriate code-point from that character set MUST be
   chosen instead.  Use of non-US-ASCII-compatible character sets is NOT
   recommended.

5.  General Syntax

5.1.  Character Set

   The default character set for an

3.  iCalendar object is UTF-8 as defined
   in RFC 2279 [9]. Object Specification

   The "charset" Content-Type parameter following sections define the details of a Calendaring and
   Scheduling Core Object Specification.  This information is intended
   to be an integral part of the MIME content type registration.  In
   addition, this information can be used in
   MIME transports to specify any other IANA registered character set.
   [[Comment.4: I think we need to say something about interoperability
   problems which result from using any other charset. --Lisa D]]

5.2.  Case Sensitivity

   All names independent of properties, property parameters, enumerated property
   values such content
   registration.  In particular, this memo has direct applicability for
   use as a calendaring and property parameter values are case-insensitive.  However,
   all other property values are case-sensitive, unless otherwise
   stated.

5.3. scheduling exchange format in file-, memory-
   or network-based transport mechanisms.

3.1.  Content Lines

   The iCalendar object is organized into individual lines of text,
   called content lines.  Content lines are delimited by a line break,
   which is a CRLF sequence (US-ASCII decimal 13, followed by US-ASCII
   decimal 10).

   Lines of text SHOULD NOT be longer than 75 octets, excluding the line
   break.  Long content lines SHOULD be split into a multiple line
   representations using the a line "folding" technique.  That is, a long
   line can be split between any two characters by inserting a CRLF
   immediately followed by a single linear white space character (i.e.,
   SPACE, US-ASCII decimal 32 or HTAB, US-ASCII decimal 9).  Any
   sequence of CRLF followed immediately by a single linear white space
   character is ignored (i.e., removed) when processing the content
   type.

   For example the line:

   DESCRIPTION:This is a long description that exists on a long line.

   Figure 1

   Can be represented as:

   DESCRIPTION:This is a lo
    ng description
     that exists on a long line.

   Figure 2

   The process of moving from this folded multiple line representation
   to its single line representation is called "unfolding".  Unfolding
   is accomplished by removing the CRLF character and the linear white
   space character that immediately follows.

   When parsing a content line, folded lines MUST first be unfolded
   according to the unfolding procedure described above.  When
   generating a content line, lines longer than 75 octets SHOULD be
   folded according to the folding procedure described above.  Content
   lines are CRLF-separated.  [[Comment.5: Removed reference

   The content information associated with an iCalendar object is
   formatted using a syntax similar to 2425
   again and simply stated that lines are defined by [RFC2425].  That
   is, the content information consists of CRLF-separated --Lisa]] content lines.

   The following ABNF notation defines the lines of content in an iCalendar
   object:

   contentline        = name *(";" param ) ":" value CRLF
   ; This ABNF is just a general definition for an initial parsing
   ; of the content line into its property name, parameter list,
   ; and value string

   ; When parsing a content line, folded lines MUST first
   ; be unfolded according to the unfolding procedure
   ; described above. When generating a content line, lines
   ; longer than 75 octets SHOULD be folded according to
   ; the folding procedure described above.

   name               = x-name / iana-token

   iana-token = 1*(ALPHA / DIGIT / "-")
   ; iCalendar identifier registered with IANA

   x-name             = "X-" [vendorid "-"] 1*(ALPHA / DIGIT / "-")
   ; Reservered Reserved for experimental use. Not intended for use in
       ; released products.

   vendorid   = 3*(ALPHA / DIGIT)     ;Vendor identification

   param              = param-name "=" param-value
                       *("," param-value)
   ; Each property defines the specific ABNF for the parameters
   ; allowed on the property. Refer to specific properties for
   ; precise parameter ABNF.

   param-name = iana-token / x-token

   param-value        = paramtext / quoted-string

   paramtext  = *SAFE-CHAR

   value      = *VALUE-CHAR

   quoted-string      = DQUOTE *QSAFE-CHAR DQUOTE

   NON-US-ASCII       = %x80-F8
   ; Use restricted by charset parameter
   ; on outer MIME object (UTF-8 preferred)

   QSAFE-CHAR = WSP / %x21 / %x23-7E / NON-US-ASCII
   ; Any character except CTLs and DQUOTE

   SAFE-CHAR  = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-7E
             / NON-US-ASCII
   ; Any character except CTLs, DQUOTE, ";", ":", ","

   VALUE-CHAR = WSP / %x21-7E / NON-US-ASCII
   ; Any textual character

   CR = %x0D
   ; carriage return

   LF = %x0A
   ; line feed

   CRLF       = CR LF
   ; Internet standard newline

   CTL        = %x00-08 / %x0A-1F / %x7F
     ; Controls

   ALPHA      = %x41-5A / %x61-7A   ; A-Z / a-z

   DIGIT      = %x30-39
     ; 0-9

   DQUOTE     = %x22
     ; Quotation Mark

   WSP        = SPACE / HTAB

   SPACE      = %x20

   HTAB       = %x09

   Figure 3

   The property value component of a content line has a format that is
   property specific.  Refer to the section describing each property for
   a definition of this format.

   All names of properties, property parameters, enumerated property
   values and property parameter values are case-insensitive.  However,
   all other property values are case-sensitive, unless otherwise
   stated.

5.4.

3.1.1.  List and Field Separators

   Some properties and parameters allow a list of values.  Values in a
   list of values MUST be separated by a COMMA character (US-ASCII
   decimal 44).  There is no significance to the order of values in a
   list.  For those parameter values (such as those that specify URI
   values) that are specified in quoted-strings, the individual quoted-
   strings are separated by a COMMA character (US-ASCII decimal 44).

   Some property values are defined in terms of multiple parts.  These
   structured property values MUST have their value parts separated by a
   SEMICOLON character (US-ASCII decimal 59).

   Some properties allow a list of parameters.  Each property parameter
   in a list of property parameters MUST be separated by a SEMICOLON
   character (US-ASCII decimal 59).

   Property parameters with values containing a COLON, a SEMICOLON or a
   COMMA character MUST be placed in quoted text.

   For example, in the following properties a SEMICOLON is used to
   separate property parameters from each other, and a COMMA is used to
   separate property values in a value list.

        ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT:MAILTO:
         jsmith@host.com

        RDATE;VALUE=DATE:19970304,19970504,19970704,19970904

5.5.

3.1.2.  Multiple Property Values

   Some properties defined in the iCalendar object can have multiple
   values.  The general rule for encoding multi-valued items is to
   simply create a new content line for each value, including the
   property name.  However, it should be noted that some properties
   support encoding multiple values in a single property by separating
   the values with a COMMA character (US-ASCII decimal 44).  Individual
   property definitions should be consulted for determining whether a
   specific property allows multiple values and in which of these two
   forms.

5.6.

3.1.3.  Binary Content

   Binary content information in an iCalendar object SHOULD be
   referenced using a URI within a property value.  That is the binary
   content information SHOULD be placed in an external MIME entity that
   can be referenced by a URI from within the iCalendar object.  In
   applications where this is not feasible, binary content information
   can be included within an iCalendar object, but only after first
   encoding it into text using the "BASE64" encoding method defined in
   [RFC 2045].
   [RFC2045].  Inline binary contact SHOULD only be used in applications
   whose special circumstances demand that an iCalendar object be
   expressed as a single entity.  A property containing inline binary
   content information MUST specify the "ENCODING" property parameter.
   Binary content information placed external to the iCalendar object
   MUST be referenced by a uniform resource identifier (URI).

   The following example specifies an "ATTACH" property that references
   an attachment external to the iCalendar object with a URI reference:

     ATTACH:http://xyz.com/public/quarterly-report.doc

     ATTACH:http://example.com/public/quarterly-report.doc

   The following example specifies an "ATTACH" property with inline
   binary encoded content information:

     ATTACH;FMTTYPE=image/basic;ENCODING=BASE64;VALUE=BINARY:
      MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQAwdzELMAkGA1U
      EBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENvbW11bmljYXRpb25zIE
         [...remainder
        <...remainder of "BASE64" encoded binary data...]

5.7. data...>

3.1.4.  Character Set

   There is not a property parameter to declare the character set used
   in a property value.  The default character set for an iCalendar
   object is UTF-8 as defined in [RFC2279].

   The "charset" Content-Type parameter can be used in MIME transports
   to specify any other IANA registered character set.

3.2.  Property Parameter Syntax Parameters

   A property can have attributes associated with it.  These "property
   parameters" contain meta-information about the property or the
   property value.  Property parameters are provided to specify such
   information as the location of an alternate text representation for a
   property value, the language of a text property value, the data type
   of the property value and other attributes.

   Property parameter values that contain the COLON (US-ASCII decimal
   58), SEMICOLON (US-ASCII decimal 59) or COMMA (US-ASCII decimal 44)
   character separators MUST be specified as quoted-string text values.
   Property parameter values MUST NOT contain the DOUBLE-QUOTE DQUOTE (US-ASCII
   decimal 22) character.  The DOUBLE-QUOTE DQUOTE (US-ASCII decimal 22) character is
   used as a delimiter for parameter values that contain restricted
   characters or URI text.  For example:

   DESCRIPTION;ALTREP="http://www.wiz.org":The Fall'98 Wild Wizards
     Conference - - Las Vegas, NV, USA
   Property parameter values that are not in quoted strings are case
   insensitive.

6.  iCalendar Objects

   The Calendaring and Scheduling Core Object is a collection of
   calendaring and scheduling information.  Typically, general property parameters defined by this information
   will consist of a single iCalendar object.  However, multiple
   iCalendar objects can be sequentially grouped together.  The first
   line and last line of the iCalendar object MUST contain a pair of
   iCalendar object delimiter strings.

   The syntax for an iCalendar object is as follows:

        icalobject = 1*("BEGIN" ":" "VCALENDAR" CRLF
                     icalbody
                     "END" ":" "VCALENDAR" CRLF)

   Figure 8

   The following is a simple example of an iCalendar object:

      BEGIN:VCALENDAR
      VERSION:2.0
      PRODID:-//hacksw/handcal//NONSGML v1.0//EN
      BEGIN:VEVENT
      DTSTART:19970714T170000Z
      DTEND:19970715T035959Z
      SUMMARY:Bastille Day Party
      END:VEVENT
      END:VCALENDAR

   Figure 9

7.  Calendar Components

   The body of an iCalendar object consists of a sequence of calendar
   properties and one or more calendar components.  The calendar
   properties are attributes that apply to the calendar as a whole.  The
   calendar components memo are collections of properties that express a
   particular calendar semantic.  For example, the calendar component
   can specify an event, a to-do, a journal entry, time zone
   information, or free/busy time information, or an alarm.

   The body of the iCalendar object is defined by
   the following notation:

        icalbody   = calprops component

        calprops

      parameter  = 2*( altrepparam           ; 'prodid' and 'version' are both REQUIRED, Alternate text representation
                 / cnparam               ; but MUST NOT occur more than once

                   prodid /version Common name
                 / cutypeparam           ; 'calscale' and 'method' are optional, Calendar user type
                 / delfromparam          ; but MUST NOT occur more than once

                   calscale Delegator
                 /
                   method deltoparam            ; Delegatee
                 /

                   x-prop

                   )

        component  = 1*(eventc dirparam              ; Directory entry
                 / todoc encodingparam         ; Inline encoding
                 / journalc fmttypeparam          ; Format type
                 / freebusyc fbtypeparam           ; Free/busy time type
                 / languageparam         ; Language for text
                 / timezonec memberparam           ; Group or list membership
                 / iana-comp partstatparam         ; Participation status
                 / x-comp)

        iana-comp rangeparam            ; Recurrence identifier range
                 / trigrelparam          ; Alarm trigger relationship
                 / reltypeparam          ; Relationship type
                 / roleparam             ; Participation role
                 / rsvpparam             ; RSVP expectation
                 / sentbyparam           ; Sent by
                 / tzidparam             ; Reference to time zone object
                 / valuetypeparam        ; Property value data type
                 / ianaparam
         ; Some other IANA registered iCalendar parameter.
                 / xparam
         ; A non-standard, experimental parameter.

      ianaparam  = "BEGIN" ":" iana-token CRLF

                     1*contentline

                     "END" ":" iana-token CRLF

        x-comp "=" param-value *("," param-value)

      xparam     = "BEGIN" ":" x-name CRLF

                     1*contentline

                     "END" ":" x-name CRLF
   Figure 10

   An iCalendar object MUST include "=" param-value *("," param-value)

3.2.1.  Alternate Text Representation

   Parameter Name: ALTREP

   Purpose: To specify an alternate text representation for the "PRODID" and "VERSION" calendar
   properties.  In addition, it MUST include at least one calendar
   component.  Special forms of iCalendar objects are possible to
   publish just busy time (i.e., only a "VFREEBUSY" calendar component)
   or time zone (i.e., only a "VTIMEZONE" calendar component)
   information.  In addition, a complex iCalendar object is possible
   that is used to capture a complete snapshot of the contents of a
   calendar (e.g., composite of many different calendar components).
   More commonly, an iCalendar object will consist of just a single
   "VEVENT", "VTODO" or "VJOURNAL" calendar component.

7.1.  Event Component

   Component Name: VEVENT

   Purpose: Provide a grouping of component properties that describe an
      event.

   Formal property
      value.

   Format Definition: A "VEVENT" calendar component The property parameter is defined by the following
      notation:

        eventc     = "BEGIN" ":" "VEVENT" CRLF
                     eventprop *alarmc
                     "END" ":" "VEVENT" CRLF

        eventprop

          altrepparam        = *(

                   ; the following are optional,
                   ; but MUST NOT occur more than once

                   class / created / description / dtstart / geo /

                   last-mod / location / organizer / priority /
                   dtstamp / seq / status / summary / transp /
                   uid / url / recurid /

                   ; either 'dtend' or 'duration' may appear in
                   ; a 'eventprop', but 'dtend' and 'duration'
                   ; MUST NOT occur in the same 'eventprop'

                   dtend / duration /

                   ; the following are optional,
                   ; and MAY occur more than once

                   attach / attendee / categories / comment /
                   contact / exdate / exrule / rstatus / related /
                   resources / rdate / rrule / x-prop

                   )

   Figure 11 "ALTREP" "=" DQUOTE uri DQUOTE
   Description: A "VEVENT" calendar component is The parameter specifies a grouping of component
   properties, and possibly including "VALARM" calendar components, URI that
   represents a scheduled amount of time on a calendar.  For example, it
   can be an activity; such as a one-hour long, department meeting from
   8:00 AM points to 9:00 AM, tomorrow.  Generally, an event will take up time
   on an individual calendar.  Hence, the event will appear as an opaque
   interval in a search for busy time.  Alternately, the event can have
   its Time Transparency set to "TRANSPARENT" in order to prevent
   blocking of the event in searches
      alternate representation for busy time.

   The "VEVENT" is also the calendar component used to specify an
   anniversary or daily reminder within a calendar.  These events have textual property value.  A property
      specifying this parameter MUST also include a
   DATE value type for the "DTSTART" property instead of that reflects
      the default
   data type representation of DATE-TIME.  If such a "VEVENT" has a "DTEND" property,
   it the text value.  The individual URI
      parameter values MUST each be specified as in a DATE value also. quoted-string.

   Example:

    DESCRIPTION;ALTREP="CID:<part3.msg.970415T083000@host.com>":Project
      XYZ Review Meeting will include the following agenda items: (a)
      Market Overview, (b) Finances, (c) Project Management

      The anniversary type of
   "VEVENT" can span more than one date (i.e, "DTEND" "ALTREP" property parameter value is
   set might point to a "text/html"
      content portion.

    Content-Type:text/html
    Content-Id:<part3.msg.970415T083000@host.com>

    <html><body>
    <p><b>Project XYZ Review Meeting</b> will include the following
    agenda items:<ol><li>Market
    Overview</li><li>Finances</li><li>Project Management</li></ol></p>
    </body></html>

3.2.2.  Common Name

   Parameter Name: CN

   Purpose: To specify the common name to be associated with the
      calendar date after user specified by the "DTSTART" property value). property.

   Format Definition: The "DTSTART" property for parameter is defined by the following
      notation:

          cnparam    = "CN" "=" param-value

   Description: This parameter can be specified on properties with a "VEVENT"
      CAL-ADDRESS value type.  The parameter specifies the inclusive start
   of common name
      to be associated with the event.  For recurring events, it also specifies the very first
   instance in calendar user specified by the recurrence set. property.
      The "DTEND" property parameter value is text.  The parameter value can be used for a "VEVENT"
      display text to be associated with the calendar component specifies address specified
      by the non-inclusive end of property.

   Example:

          ORGANIZER;CN="John Smith":MAILTO:jsmith@host.com

3.2.3.  Calendar User Type

   Parameter Name: CUTYPE

   Purpose: To specify the event.  For
   cases where a "VEVENT" calendar component specifies a "DTSTART"
   property with a DATE data type but no "DTEND" property, of calendar user specified by the events
   non-inclusive end
      property.

   Format Definition: The property parameter is defined by the end following
      notation:

      cutypeparam        = "CUTYPE" "="
                          ("INDIVIDUAL"        ; An individual
                         / "GROUP"             ; A group of individuals
                         / "RESOURCE"          ; A physical resource
                         / "ROOM"              ; A room resource
                         / "UNKNOWN"           ; Otherwise not known
                         / x-name              ; Experimental type
                         / iana-token)         ; Other IANA registered
                                               ; type
      ; Default is INDIVIDUAL

   Description: This parameter can be specified on properties with a
      CAL-ADDRESS value type.  The parameter identifies the type of
      calendar date user specified by the
   "DTSTART" property.  For cases where a "VEVENT" calendar component
   specifies  If not specified on a "DTSTART"
      property with a DATE-TIME data type but no
   "DTEND" property, that allows this parameter, the event ends on default is INDIVIDUAL.

   Example:

          ATTENDEE;CUTYPE=GROUP:MAILTO:ietf-calsch@imc.org

3.2.4.  Delegators

   Parameter Name: DELEGATED-FROM

   Purpose: To specify the same calendar date and time
   of day users that have delegated their
      participation to the calendar user specified by the "DTSTART" property.

   Format Definition: The "VEVENT" calendar component cannot property parameter is defined by the following
      notation:

    delfromparam       = "DELEGATED-FROM" "=" DQUOTE cal-address DQUOTE
                         *("," DQUOTE cal-address DQUOTE)

   Description: This parameter can be nested within another
   calendar component.  However, "VEVENT" calendar components specified on properties with a
      CAL-ADDRESS value type.  This parameter can be
   related to each other or to specified on a "VTODO"
      property that has a value type of calendar address.  This
      parameter specifies those calendar users that have delegated their
      participation in a group scheduled event or to-do to a "VJOURNAL" the calendar
   component with
      user specified by the "RELATED-TO" property.

   Example 1:  The following is an example of the "VEVENT" calendar
   component used to represent a meeting that will also value MUST be opaque to
   searches for busy time:

        BEGIN:VEVENT
        UID:19970901T130000Z-123401@host.com
        DTSTAMP:19970901T1300Z
        DTSTART:19970903T163000Z
        DTEND:19970903T190000Z
        SUMMARY:Annual Employee Review
        CLASS:PRIVATE
        CATEGORIES:BUSINESS,HUMAN RESOURCES
        END:VEVENT

   Figure 12
   Example 2: a MAILTO URI as
      defined in [RFC1738].  The following is an example of the "VEVENT" individual calendar
   component used to represent a reminder that will not address parameter
      values MUST each be opaque, but
   rather transparent, to searches for busy time:

        BEGIN:VEVENT
        UID:19970901T130000Z-123402@host.com
        DTSTAMP:19970901T1300Z
        DTSTART:19970401T163000Z
        DTEND:19970402T010000Z
        SUMMARY:Laurel is specified in sensitivity awareness class.
        CLASS:PUBLIC
        CATEGORIES:BUSINESS,HUMAN RESOURCES
        TRANSP:TRANSPARENT
        END:VEVENT

   Figure 13

   Example 3: The following is an example of a quoted-string.

   Example:

          ATTENDEE;DELEGATED-FROM="MAILTO:jsmith@host.com":MAILTO:
           jdoe@host.com

3.2.5.  Delegatees

   Parameter Name: DELEGATED-TO

   Purpose: To specify the "VEVENT" calendar
   component used users to represent an anniversary that will occur annually.
   Since it takes up no time, it will not appear as opaque in a search
   for busy time; no matter what whom the value of calendar user
      specified by the "TRANSP" property
   indicates:

        BEGIN:VEVENT
        UID:19970901T130000Z-123403@host.com
        DTSTAMP:19970901T1300Z
        DTSTART:19971102
        SUMMARY:Our Blissful Anniversary
        CLASS:CONFIDENTIAL
        CATEGORIES:ANNIVERSARY,PERSONAL,SPECIAL OCCASION
        RRULE:FREQ=YEARLY
        END:VEVENT

   Figure 14

7.2.  To-do Component

   Component Name: VTODO

   Purpose: Provide a grouping of calendar properties that describe a
   to-do.

   Formal has delegated participation.

   Format Definition: A "VTODO" calendar component The property parameter is defined by the following
      notation:

        todoc

          deltoparam = "BEGIN" ":" "VTODO" CRLF
                     todoprop *alarmc
                     "END" ":" "VTODO" CRLF

        todoprop   = *(

                   ; the following are optional,
                   ; but MUST NOT occur more than once

                   class / completed / created / description / dtstamp /
                   dtstart / geo / last-mod / location / organizer /
                   percent / priority / recurid / seq / status /
                   summary / uid / url /

                   ; either 'due' or 'duration' may appear in
                   ; a 'todoprop', but 'due' and 'duration'
                   ; MUST NOT occur in the same 'todoprop'

                   due / duration /

                   ; the following are optional,
                   ; and MAY occur more than once
                   attach / attendee / categories / comment / contact /
                   exdate / exrule / rstatus / related / resources /
                   rdate / rrule / x-prop

                   )

   Figure 15 "DELEGATED-TO" "=" DQUOTE cal-address DQUOTE
                       *("," DQUOTE cal-address DQUOTE)

   Description: A "VTODO" calendar component is a grouping of component This parameter can be specified on properties and possibly "VALARM" with a
      CAL-ADDRESS value type.  This parameter specifies those calendar components that represent
   an action-item
      users whom have been delegated participation in a group scheduled
      event or assignment.  For example, it can to-do by the calendar user specified by the property.
      The value MUST be used to
   represent an item of work assigned to an individual; such a MAILTO URI as "turn defined in
   travel expense today". [RFC1738].  The "VTODO" calendar component cannot be nested within another
   calendar component.  However, "VTODO"
      individual calendar components can be
   related to address parameter values MUST each other or to be
      specified in a "VTODO" or quoted-string.

   Example:

          ATTENDEE;DELEGATED-TO="MAILTO:jdoe@host.com","MAILTO:jqpublic@
           host.com":MAILTO:jsmith@host.com

3.2.6.  Directory Entry Reference

   Parameter Name: DIR

   Purpose: To specify reference to a "VJOURNAL" calendar
   component directory entry associated with
      the "RELATED-TO" property.

   A "VTODO" calendar component without user specified by the "DTSTART" and "DUE" (or
   "DURATION") property.

   Format Definition: The property parameter is defined by the following
      notation:

          dirparam   = "DIR" "=" DQUOTE uri DQUOTE
   Description: This parameter can be specified on properties with a
      CAL-ADDRESS value type.  The parameter specifies a to-do that will be reference to
      the directory entry associated with
   each successive the calendar date, until it is completed.

   Example: user specified by
      the property.  The following parameter value is an example of a "VTODO" calendar component:

        BEGIN:VTODO
        UID:19970901T130000Z-123404@host.com
        DTSTAMP:19970901T1300Z
        DTSTART:19970415T133000Z
        DUE:19970416T045959Z
        SUMMARY:1996 Income Tax Preparation
        CLASS:CONFIDENTIAL
        CATEGORIES:FAMILY,FINANCE
        PRIORITY:1
        STATUS:NEEDS-ACTION
        END:VTODO

   Figure 16

7.3.  Journal Component

   Component URI.  The individual URI
      parameter values MUST each be specified in a quoted-string.

   Example:

      ORGANIZER;DIR="ldap://host.com:6666/o=eDABC%20Industries,c=3DUS??
       (cn=3DBJim%20Dolittle)":MAILTO:jimdo@host1.com

3.2.7.  Inline Encoding

   Parameter Name: VJOURNAL ENCODING

   Purpose: Provide a grouping of component properties that describe a
   journal entry.

   Formal To specify an alternate inline encoding for the property
      value.

   Format Definition: A "VJOURNAL" calendar component The property parameter is defined by the following
      notation:

        journalc   = "BEGIN" ":" "VJOURNAL" CRLF
                     jourprop
                     "END" ":" "VJOURNAL" CRLF

        jourprop

          encodingparam      = *(

                   ; the following are optional, "ENCODING" "="
                               ("8BIT"
             ; but MUST NOT occur more than once

                   class / created / description / dtstart / dtstamp /
                   last-mod / organizer / recurid / seq / status /
                   summary "8bit" text encoding is defined in [RFC2045]
                             / uid "BASE64"
             ; "BASE64" binary encoding format is defined in [RFC2045]
                             / url iana-token
             ; Some other IANA registered iCalendar encoding type
                             / x-name)
             ; A non-standard, experimental encoding type

   Description: The property parameter identifies the following are optional,
                   ; and MAY occur more than once

                   attach / attendee / categories / comment /
                   contact / exdate / exrule / related / rdate /
                   rrule / rstatus / x-prop

                   )

   Figure 17

   Description: A "VJOURNAL" calendar component inline encoding
      used in a property value.  The default encoding is "8BIT",
      corresponding to a grouping property value consisting of
   component properties that represent one or more descriptive text
   notes associated with a particular calendar date. text.  The "DTSTART"
   property is used
      "BASE64" encoding type corresponds to specify a property value encoded
      using the calendar date that "BASE64" encoding defined in [RFC2045].

      If the journal entry
   is associated with.  Generally, it will have a DATE value data type,
   but it can also type parameter is ";VALUE=BINARY", then the inline
      encoding parameter MUST be used to specify a DATE-TIME specified with the value data type.
   Examples of a journal entry include a daily record of a legislative
   body or a journal entry
      ";ENCODING=BASE64".

   Example:

          ATTACH;FMTYPE=IMAGE/JPEG;ENCODING=BASE64;VALUE=BINARY:MIICajC
           CAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQAwdzELMAkGA1UEBhMCVVMxLDA
           qBgNVBAoTI05ldHNjYXBlIENvbW11bmljYXRpb25zIENvcnBvcmF0aW9uMRw
           <...remainder of individual telephone contacts for "BASE64" encoded binary data...>

3.2.8.  Format Type

   Parameter Name: FMTTYPE

   Purpose: To specify the day
   or an ordered list content type of accomplishments for the day. a referenced object.

   Format Definition: The "VJOURNAL"
   calendar component property parameter is defined by the following
      notation:

    fmttypeparam       = "FMTTYPE" "=" iana-token
                                       ; A IANA registered content type
                                    / x-name
                                       ; A non-standard content type

   Description: This parameter can also be specified on properties that are
      used to associate a document with a
   calendar date. reference an object.  The "VJOURNAL" calendar component does not take up time parameter specifies the content
      type of the referenced object.  For example, on the "ATTACH"
      property, a
   calendar.  Hence, it does not play a role in free or busy time
   searches - - it is as though it has a time transparency FTP type URI value does not, by itself, necessarily
      convey the type of
   TRANSPARENT.  It is transparent to any such searches.

   The "VJOURNAL" calendar component cannot be nested within another
   calendar component.  However, "VJOURNAL" calendar components can be
   related to each other or to a "VEVENT" or to a "VTODO" calendar
   component, content associated with the "RELATED-TO" property.

   Example: resource.  The following is an example of
      parameter value MUST be the "VJOURNAL" calendar
   component:

     BEGIN:VJOURNAL
     UID:19970901T130000Z-123405@host.com
     DTSTAMP:19970901T1300Z
     DTSTART;VALUE=DATE:19970317
     SUMMARY:Staff meeting minutes
     DESCRIPTION:1. Staff meeting: Participants include Joe\, Lisa
      and Bob. Aurora project plans were reviewed. There is currently
      no budget reserves TEXT for this project. Lisa will escalate to
      management. Next meeting on Tuesday.\n
      2. Telephone Conference: ABC Corp. sales representative called
      to discuss new printer. Promised to get us a demo by Friday.\n
      3. Henry Miller (Handsoff Insurance): Car was totaled by tree.
      Is looking into either an IANA registered
      content type or a loaner car. 654-2323 (tel).
     END:VJOURNAL

   Figure 18

7.4. non-standard content type.

   Example:

           ATTACH;FMTTYPE=application/msword:ftp://domain.com/pub/docs/
            agenda.doc

3.2.9.  Free/Busy Component

   Component Time Type

   Parameter Name: VFREEBUSY FBTYPE

   Purpose: Provide a grouping of component properties that describe
   either a request for free/busy time, describe a response to a request
   for free/busy time To specify the free or describe a published set of busy time.

   Formal time type.

   Format Definition: A "VFREEBUSY" calendar component The property parameter is defined by the following
      notation:

        freebusyc  = "BEGIN" ":" "VFREEBUSY" CRLF
                     fbprop
                     "END" ":" "VFREEBUSY" CRLF

        fbprop

          fbtypeparam        = *(

                   ; the following are optional,
                   ; but MUST NOT occur more than once

                   contact "FBTYPE" "=" ("FREE" / dtstart "BUSY"
                             / dtend "BUSY-UNAVAILABLE" / duration "BUSY-TENTATIVE"
                             / dtstamp x-name
             ; Some experimental iCalendar data type.
                             /
                   organizer / uid / url /

                   ; the following are optional, iana-token)
             ; and MAY occur more than once

                   attendee / comment / freebusy / rstatus / x-prop

                   )

   Figure 19 Some other IANA registered iCalendar data type.

   Description: A "VFREEBUSY" calendar component is a grouping of
   component properties that represents either a request for, a reply to
   a request for The parameter specifies the free or busy time information or a published set of
   busy time information.

   When used to request free/busy time information, the "ATTENDEE"
   property specifies type.  The
      value FREE indicates that the calendar users whose free/busy time interval is being
   requested; the "ORGANIZER" property specifies free for
      scheduling.  The value BUSY indicates that the calendar user who time interval is requesting the free/busy time;
      busy because one or more events have been scheduled for that
      interval.  The value BUSY-UNAVAILABLE indicates that the "DTSTART" time
      interval is busy and "DTEND"
   properties specify that the window of time for which interval can not be scheduled.  The
      value BUSY-TENTATIVE indicates that the free/busy time interval is
   being requested; the "UID" and "DTSTAMP" properties are busy
      because one or more events have been tentatively scheduled for
      that interval.  If not specified to
   assist in proper sequencing on a property that allows this
      parameter, the default is BUSY.

   Example: The following is an example of multiple free/busy time requests.

   When used to reply to this parameter on a request for free/busy time, FREEBUSY
      property.

          FREEBUSY;FBTYPE=BUSY:19980415T133000Z/19980415T170000Z

3.2.10.  Language

   Parameter Name: LANGUAGE

   Purpose: To specify the "ATTENDEE" language for text values in a property specifies or
      property parameter.

   Format Definition: The property parameter is defined by the calendar user responding to following
      notation:

    languageparam =    "LANGUAGE" "=" language

    language = <Text identifying a language, as defined in [RFC1766]>

   Description: This parameter can be specified on properties with a
      text value type.  The parameter identifies the free/busy time
   request; language of the
      text in the "ORGANIZER" property specifies or property parameter value.  The value of
      the calendar user "language" property parameter is that
   originally requested defined in [RFC1766].

      For transport in a MIME entity, the free/busy time; Content-Language header field
      can be used to set the "FREEBUSY" property
   specifies default language for the free/busy time information (if it exists); and entire body part.
      Otherwise, no default language is assumed.

   Example:

          SUMMARY;LANGUAGE=us-EN:Company Holiday Party

          LOCATION;LANGUAGE=en:Germany

          LOCATION;LANGUAGE=no:Tyskland

      The following example makes use of the

   "UID" and "DTSTAMP" properties are specified to assist Quoted-Printable encoding
      in proper
   sequencing of multiple free/busy time replies.

   When used order to publish busy time, represent non-ASCII characters.

          LOCATION;LANGUAGE=3Dda:K=C3=B8benhavn

          LOCATION;LANGUAGE=en:Copenhagen

3.2.11.  Group or List Membership

   Parameter Name: MEMBER

   Purpose: To specify the "ORGANIZER" property specifies group or list membership of the calendar user associated with
      specified by the published busy time; property.

   Format Definition: The property parameter is defined by the
   "DTSTART" and "DTEND" following
      notation:

          memberparam        = "MEMBER" "=" DQUOTE cal-address DQUOTE
                               *("," DQUOTE cal-address DQUOTE)

   Description: This parameter can be specified on properties specify an inclusive time window
   that surrounds the busy time information; the "FREEBUSY" property
   specifies with a
      CAL-ADDRESS value type.  The parameter identifies the published busy time information; and groups or
      list membership for the "DTSTAMP"
   property specifies calendar user specified by the date/time that iCalendar object was created. property.
      The "VFREEBUSY" calendar component cannot be nested within another
   calendar component.  Multiple "VFREEBUSY" parameter value either a single calendar components can be
   specified within an iCalendar object.  This permits the grouping of
   Free/Busy information into logical collections, such as monthly
   groups of busy time information.

   The "VFREEBUSY" calendar component is intended for use address in iCalendar
   object methods involving requests for free time, requests for busy
   time, requests for both free and busy, and the associated replies.

   Free/Busy information is represented with the "FREEBUSY" property.
   This property provides a terse representation of time periods.  One quoted-
      string or more "FREEBUSY" properties can be specified in the "VFREEBUSY" a COMMA character (US-ASCII decimal 44) list of calendar component.

   When present
      addresses, each in a "VFREEBUSY" quoted-string.  The individual calendar component, the "DTSTART" and
   "DTEND" properties SHOULD
      address parameter values MUST each be specified prior to any "FREEBUSY"
   properties.  In a free time request, these properties can be used in
   combination with the "DURATION" property to represent a request for a
   duration of free time within a specified window of time.

   The recurrence properties ("RRULE", "EXRULE", "RDATE", "EXDATE") are
   not permitted within a "VFREEBUSY" calendar component.  Any recurring
   events are resolved into their individual busy time periods using the
   "FREEBUSY" property.

   Example 1: The following is an example of a "VFREEBUSY" calendar
   component used to request free or busy time information:

        BEGIN:VFREEBUSY
        ORGANIZER:MAILTO:jane_doe@host1.com
        ATTENDEE:MAILTO:john_public@host2.com
        DTSTART:19971015T050000Z
        DTEND:19971016T050000Z
        DTSTAMP:19970901T083000Z
        END:VFREEBUSY

   Figure 20
   Example 2: A "VFREEBUSY" calendar component used to reply to quoted-
      string.

   Example:

    ATTENDEE;MEMBER="MAILTO:ietf-calsch@imc.org":MAILTO:jsmith@host.com

    ATTENDEE;MEMBER="MAILTO:projectA@host.com","MAILTO:projectB@host.
     com":MAILTO:janedoe@host.com

3.2.12.  Participation Status

   Parameter Name: PARTSTAT

   Purpose: To specify the
   request with busy time information.

        BEGIN:VFREEBUSY
        ORGANIZER:MAILTO:jane_doe@host1.com
        ATTENDEE:MAILTO:john_public@host2.com
        DTSTAMP:19970901T100000Z
        FREEBUSY;VALUE=PERIOD:19971015T050000Z/PT8H30M,
         19971015T160000Z/PT5H30M,19971015T223000Z/PT6H30M
        URL:http://host2.com/pub/busy/jpublic-01.ifb
        COMMENT:This iCalendar file contains busy time information participation status for the next three months.
        END:VFREEBUSY

   Figure 21

   Example 3: a "VFREEBUSY" calendar component used to publish busy time
   information.

        BEGIN:VFREEBUSY
        ORGANIZER:jsmith@host.com
        DTSTART:19980313T141711Z
        DTEND:19980410T141711Z
        FREEBUSY:19980314T233000Z/19980315T003000Z
        FREEBUSY:19980316T153000Z/19980316T163000Z
        FREEBUSY:19980318T030000Z/19980318T040000Z
        URL:http://www.host.com/calendar/busytime/jsmith.ifb
        END:VFREEBUSY

   Figure 22

7.5.  Time Zone Component

   Component Name: VTIMEZONE

   Purpose: Provide a grouping of component properties that defines a
   time zone.

   Formal user
      specified by the property.

   Format Definition: A "VTIMEZONE" calendar component The property parameter is defined by the following
      notation:

        timezonec

    partstatparam      = "BEGIN" ":" "VTIMEZONE" CRLF

                     2*( "PARTSTAT" "="
                        ("NEEDS-ACTION"        ; 'tzid' is required, but MUST NOT occur more Event needs action
                       / "ACCEPTED"            ; than once
                   tzid Event accepted
                       / "DECLINED"            ; 'last-mod' and 'tzurl' are optional,
                   but MUST NOT occur more than once

                   last-mod Event declined
                       / tzurl "TENTATIVE"           ; Event tentatively
                                               ; accepted
                       / "DELEGATED"           ; one of 'standardc' or 'daylightc' MUST occur
                   ..; and each MAY occur more than once.

                   standardc Event delegated
                       / daylightc x-name                ; Experimental status
                       / iana-token)           ; the following is optional, Other IANA registered
                                               ; and MAY occur more than once

                     x-prop

                     )

                     "END" ":" "VTIMEZONE" CRLF

        standardc  = "BEGIN" ":" "STANDARD" CRLF

                     tzprop

                     "END" ":" "STANDARD" CRLF

        daylightc  = "BEGIN" ":" "DAYLIGHT" CRLF

                     tzprop

                     "END" ":" "DAYLIGHT" CRLF

        tzprop     = 3*( status
    ; the following These are each REQUIRED, the participation statuses for a "VEVENT". Default is
    ; but MUST NOT occur more than once

                   dtstart NEEDS-ACTION
    partstatparam      /= "PARTSTAT" "="
                        ("NEEDS-ACTION"        ; To-do needs action
                       / tzoffsetto "ACCEPTED"            ; To-do accepted
                       / tzoffsetfrom "DECLINED"            ; To-do declined
                       / "TENTATIVE"           ; the following are optional, To-do tentatively
                                               ; and MAY occur more than once

                   comment / rdate accepted
                       / rrule "DELEGATED"           ; To-do delegated
                       / tzname "COMPLETED"           ; To-do completed.
                                               ; COMPLETED property has
                                               ;date/time completed.
                       / x-prop

                   )
   Figure 23

   Description: A time zone is unambiguously defined by the set "IN-PROCESS"          ; To-do in process of time
   measurement rules determined by
                                               ; being completed
                       / x-name                ; Experimental status
                       / iana-token)           ; Other IANA registered
                                               ; status
    ; These are the governing body participation statuses for a given
   geographic area. "VTODO". Default is
    ; NEEDS-ACTION

    partstatparam      /= "PARTSTAT" "="
                        ("NEEDS-ACTION"        ; Journal needs action
                       / "ACCEPTED"            ; Journal accepted
                       / "DECLINED"            ; Journal declined
                       / x-name                ; Experimental status
                       / iana-token)           ; Other IANA registered
                                               ; status
    ; These rules describe at are the participation statuses for a minimum "VJOURNAL". Default is
    ; NEEDS-ACTION

   Description: This parameter can be specified on properties with a
      CAL-ADDRESS value type.  The parameter identifies the base offset
   from UTC
      participation status for the time zone, often referred to as calendar user specified by the Standard Time
   offset.  Many locations adjust their Standard Time forward
      property value.  The parameter values differ depending on whether
      they are associated with a group scheduled "VEVENT", "VTODO" or
   backward by
      "VJOURNAL".  The values MUST match one hour, in order to accommodate seasonal changes in
   number of daylight hours, often referred to as Daylight Saving Time.
   Some locations adjust their time by the values allowed for
      the given calendar component.  If not specified on a fraction of an hour.  Standard
   Time is also known as Winter Time.  Daylight Saving Time property that
      allows this parameter, the default value is also
   known as Advanced Time, Summer Time, or Legal Time in certain
   countries. NEEDS-ACTION.

   Example:

          ATTENDEE;PARTSTAT=DECLINED:MAILTO:jsmith@host.com

3.2.13.  Recurrence Identifier Range

   Parameter Name: RANGE

   Purpose: To specify the effective range of recurrence instances from
      the instance specified by the recurrence identifier specified by
      the property.

   Format Definition: The property parameter is defined by the following table shows
      notation:

    rangeparam = "RANGE" "=" ("THISANDPRIOR"
       ; To specify all instances prior to the changes in time zone rules
   in effect for New York City starting from 1967.  Each line represents recurrence identifier
               / "THISANDFUTURE")
       ; To specify the instance specified by the recurrence identifier
       ; and all subsequent recurrence instances

   Description: The parameter can be specified on a description or rule for property that
      specifies a particular observance.

                         Effective Observance Rule

      +-----------+-------------------------+--------+--------------+
      | Date      | (Date/Time)             | Offset | Abbreviation |
      +-----------+-------------------------+--------+--------------+
      | 1967-*    | last Sun in Oct, 02:00  | -0500  | EST          |
      |           |                         |        |              |
      | 1967-1973 | last Sun in Apr, 02:00  | -0400  | EDT          |
      |           |                         |        |              |
      | 1974-1974 | Jan 6, 02:00            | -0400  | EDT          |
      |           |                         |        |              |
      | 1975-1975 | Feb 23, 02:00           | -0400  | EDT          |
      |           |                         |        |              |
      | 1976-1986 | last Sun in Apr, 02:00  | -0400  | EDT          |
      |           |                         |        |              |
      | 1987-*    | first Sun in Apr, 02:00 | -0400  | EDT          |
      +-----------+-------------------------+--------+--------------+

   Note: recurrence identifier.  The specification parameter specifies the
      effective range of a global time zone registry recurrence instances that is not
   addressed specified by this document and the
      property.  The effective range is left for future study.  However,
   implementers may find from the Olson time zone database [TZ] a useful
   reference.  It recurrence identified
      specified by the property.  If this parameter is not specified an informal, public-domain collection of time zone
   information, which
      allowed property, then the default range is currently being maintained the single instance
      specified by volunteer
   Internet participants, and is used in several operating systems.
   This database contains current and historical time zone information
   for a wide variety of locations around the globe; it provides a time
   zone recurrence identifier for every unique time zone rule set in actual use
   since 1970, with historical data going back value of the property.  The
      parameter value can be "THISANDPRIOR" to indicate a range defined
      by the introduction recurrence identified value of
   standard time.

   Interoperability between two calendaring and scheduling applications,
   especially for recurring events, to-dos or journal entries, is
   dependent on the ability to capture and convey date property and time
   information in an unambiguous format. all prior
      instances.  The specification of current
   time zone information is integral parameter value can also be "THISANDFUTURE" to this behavior.

   If present,
      indicate a range defined by the "VTIMEZONE" calendar component defines recurrence identifier and all
      subsequent instances.

   Example:

          RECURRENCE-ID;RANGE=THISANDPRIOR:19980401T133000Z

3.2.14.  Alarm Trigger Relationship

   Parameter Name: RELATED

   Purpose: To specify the set relationship of
   Standard Time and Daylight Saving Time observances (or rules) for a
   particular time zone for a given interval the alarm trigger with
      respect to the start or end of time.  The "VTIMEZONE"
   calendar component cannot be nested within other calendar components.
   Multiple "VTIMEZONE" the calendar components can exist in an iCalendar
   object.  In this situation, each "VTIMEZONE" MUST represent a unique
   time zone definition.  This component.

   Format Definition: The property parameter is necessary for some classes defined by the following
      notation:

          trigrelparam       = "RELATED" "="
                              ("START"       ; Trigger off of events,
   such as airline flights, that start in one time zone and
                             / "END")        ; Trigger off of end in
   another.

   Description: The "VTIMEZONE" calendar component MUST parameter can be present if the iCalendar
   object contains an RRULE that generates dates specified on both sides of properties that
      specify an alarm trigger with a time
   zone shift (e.g. both in Standard Time and Daylight Saving Time)
   unless DURATION value type.  The
      parameter specifies whether the iCalendar object intends alarm will trigger relative to convey a floating time (See
   Section 13.13 for proper interpretation the
      start or end of floating time).  It can be
   present if the iCalendar object does not contain such a RRULE.  In
   addition, if a RRULE is present, there MUST be valid time zone
   information for all recurrence instances.

   The "VTIMEZONE" calendar component MUST include the "TZID" property
   and at least one definition of a standard or daylight component.  The
   standard or daylight component MUST include the "DTSTART",
   "TZOFFSETFROM" and "TZOFFSETTO" properties.

   An individual "VTIMEZONE" calendar component MUST be specified for
   each unique "TZID" parameter value specified in START
      will set the iCalendar object.

   Each "VTIMEZONE" calendar component consists of a collection of one
   or more sub-components that describe alarm to trigger off the rule for a particular
   observance (either a Standard Time or a Daylight Saving Time
   observance).  The "STANDARD" sub-component consists of a collection
   of properties that describe Standard Time.  The "DAYLIGHT" sub-
   component consists of a collection of properties that describe
   Daylight Saving Time.  In general this collection start of properties
   consists of: the first onset date-time for the observance

      the last onset date-time for calendar
      component; the observance, if a last onset is
      known. parameter value END will set the offset alarm to be applied for trigger
      off the observance
      a rule that describes end of the day and time when calendar component.  If the observance takes
      effect parameter is not
      specified on an optional name for the observance

   For a given time zone, there may be multiple unique definitions of allowable property, then the observances over a period of time.  Each observance is described
   using either a "STANDARD" or "DAYLIGHT" sub-component.  The
   collection of these sub-components default is used to describe START.

   Example:

          TRIGGER;RELATED=END:PT5M

3.2.15.  Relationship Type

   Parameter Name: RELTYPE

   Purpose: To specify the time zone
   for a given period type of time. hierarchical relationship associated
      with the calendar component specified by the property.

   Format Definition: The offset to apply at any given time property parameter is
   found defined by locating the observance following
      notation:

      reltypeparam       = "RELTYPE" "="
                          ("PARENT"      ; Parent relationship. Default.
                         / "CHILD"       ; Child relationship
                         / "SIBLING      ; Sibling relationship
                         / iana-token    ; Some other IANA registered
                                         ; iCalendar relationship type
                         / x-name)       ; A non-standard, experimental
                                         ; relationship type

   Description: This parameter can be specified on a property that has the last onset date and
   time before
      references another related calendar.  The parameter specifies the time in question, and using
      hierarchical relationship type of the offset value from
   that observance.

   The top-level properties in a "VTIMEZONE" calendar component are:
      referenced by the property.  The mandatory "TZID" property is a text parameter value can be PARENT, to
      indicate that uniquely
   identifies the VTIMZONE referenced calendar component within the scope of an
   iCalendar object.

   The optional "LAST-MODIFIED" property is a UTC value superior of
      calendar component; CHILD to indicate that specifies the date and time that this time zone definition was last updated.

   The optional "TZURL" property referenced calendar
      component is url value that points to a published
   VTIMEZONE definition.  TZURL SHOULD refer subordinate of the calendar component; SIBLING to a resource
      indicate that is
   accessible by anyone who might need to interpret the object.  This
   SHOULD NOT normally be referenced calendar component is a file: URL or other URL that peer of the
      calendar component.  If this parameter is not widely-
   accessible.

   The collection of properties that are used to define specified on an
      allowable property, the STANDARD and
   DAYLIGHT sub-components include:

   The mandatory "DTSTART" property gives default relationship type is PARENT.

   Example:

      RELATED-TO;RELTYPE=SIBLING:<19960401-080045-4000F192713@host.com>

3.2.16.  Participation Role

   Parameter Name: ROLE

   Purpose: To specify the effective onset date and
   local time participation role for the time zone sub-component definition.  "DTSTART" in
   this usage MUST be calendar user
      specified as a local DATE-TIME value. by the property.

   Format Definition: The mandatory "TZOFFSETFROM" property gives the UTC offset which parameter is
   in use when defined by the onset following
      notation:

    roleparam  = "ROLE" "="
                ("CHAIR"               ; Indicates chair of this time zone observance begins.
   "TZOFFSETFROM" the
                                       ; calendar entity
               / "REQ-PARTICIPANT"     ; Indicates a participant whose
                                       ; participation is combined required
               / "OPT-PARTICIPANT"     ; Indicates a participant whose
                                       ; participation is optional
               / "NON-PARTICIPANT"     ; Indicates a participant who is
                                       ; copied for information
                                       ; purposes only
               / x-name                ; Experimental role
               / iana-token)           ; Other IANA role
    ; Default is REQ-PARTICIPANT

   Description: This parameter can be specified on properties with "DTSTART" to define a
      CAL-ADDRESS value type.  The parameter specifies the effective
   onset participation
      role for the time zone sub-component definition.  For example, the
   following represents the time at which calendar user specified by the observance of Standard
   Time took effect property in Fall 1967 for New York City:

        DTSTART:19671029T020000

        TZOFFSETFROM:-0400

   Figure 24
   The mandatory "TZOFFSETTO " property gives the UTC offset for the
   time zone sub-component (Standard Time or Daylight Saving Time) when group
      schedule calendar component.  If not specified on a property that
      allows this observance parameter, the default value is in use. REQ-PARTICIPANT.

   Example:

          ATTENDEE;ROLE=CHAIR:MAILTO:mrbig@host.com

3.2.17.  RSVP Expectation

   Parameter Name: RSVP

   Purpose: To specify whether there is an expectation of a favor of a
      reply from the calendar user specified by the property value.

   Format Definition: The optional "TZNAME" property parameter is defined by the customary name for the time
   zone.  It may following
      notation:

          rsvpparam = "RSVP" "=" ("TRUE" / "FALSE")
          ; Default is FALSE

   Description: This parameter can be specified multiple times, to allow for specifying
   multiple language variants on properties with a
      CAL-ADDRESS value type.  The parameter identifies the expectation
      of a reply from the time zone names. calendar user specified by the property value.
      This could be parameter is used for displaying dates. by the "Organizer" to request a
      participation status reply from an "Attendee" of a group scheduled
      event or to-do.  If specified, not specified on a property that allows this
      parameter, the onset for default value is FALSE.

   Example:

          ATTENDEE;RSVP=TRUE:MAILTO:jsmith@host.com

3.2.18.  Sent By

   Parameter Name: SENT-BY

   Purpose: To specify the observance defined calendar user that is acting on behalf of the
      calendar user specified by the time zone
   sub-component property.

   Format Definition: The property parameter is defined by either the "RRULE" or "RDATE" property.
   If neither is specified, only one sub-component following
      notation:

          sentbyparam        = "SENT-BY" "=" DQUOTE cal-address DQUOTE

   Description: This parameter can be specified in on properties with a
      CAL-ADDRESS value type.  The parameter specifies the "VTIMEZONE" calendar component and it is assumed user
      that is acting on behalf of the single
   observance calendar user specified is always by the
      property.  The parameter value MUST be a MAILTO URI as defined in effect.
      [RFC1738].  The "RRULE" property defines individual calendar address parameter values MUST
      each be specified in a quoted-string.

   Example:

        ORGANIZER;SENT-BY:"MAILTO:sray@host.com":MAILTO:jsmith@host.com

3.2.19.  Time Zone Identifier

   Parameter Name: TZID
   Purpose: To specify the recurrence rule identifier for the onset of the
   observance defined by this time zone sub-component.  Some specific
   requirements definition for a
      time component in the usage of RRULE for this purpose include:

      If observance property value.

   Format Definition: The property parameter is known to have an effective end date, defined by the "UNTIL"
      recurrence rule following
      notation:

          tzidparam  = "TZID" "=" [tzidprefix] paramtext CRLF

          tzidprefix = "/"

   Description: The parameter MUST be used to specify specified on the last valid
      onset of this observance (i.e., "DTSTART",
      "DTEND", "DUE", "EXDATE" and "RDATE" properties when either a
      DATE- TIME or TIME value type is specified and when the UNTIL date-time will be equal value is
      not either a UTC or a "floating" time.  Refer to the last instance generated by the recurrence pattern).  It
      MUST be specified in DATE-TIME or
      TIME value type definition for a description of UTC time.

      The "DTSTART" and "floating
      time" formats.  This property parameter specifies a text value
      which uniquely identifies the "TZOFFSETTO" properties MUST "VTIMEZONE" calendar component to be
      used when
      generating evaluating the onset date-time values (instances) from time portion of the RRULE.

   Alternatively, property.  The value
      of the "RDATE" TZID property can parameter will be used equal to define the onset value of the observance by giving
      TZID property for the matching time zone definition.  An
      individual onset date and times.
   "RDATE" in this usage MUST be "VTIMEZONE" calendar component MUST be specified as for
      each unique "TZID" parameter value specified in the iCalendar
      object.

      The parameter MUST be specified on properties with a local DATE-TIME
      value in if the DATE-TIME is not either a UTC or a "floating" time.

      The optional "COMMENT" property is also allowed for descriptive
   explanatory text.

   Example: The following are examples presence of the "VTIMEZONE" calendar
   component:

   Example 1: Time zone information for the Eastern United States using
   "RDATE" property.  Note SOLIDUS character (US-ASCII decimal 47) as a
      prefix, indicates that this is only suitable for TZID represents a recurring
   event that starts on or later than April 6, 1997 at 03:00:00 EDT
   (i.e., the earliest effective transition date and time) and ends no
   later than April 7, 1998 02:00:00 EST (i.e., latest valid date and
   time for EST unique ID in this scenario).  For example, this can be used for a
   recurring event that occurs every Friday, 8am-9:00 AM, starting June
   1, 1997, ending December 31, 1997.

        BEGIN:VTIMEZONE
        TZID:US-Eastern
        LAST-MODIFIED:19870101T000000Z
        BEGIN:STANDARD
        DTSTART:19971026T020000
        RDATE:19971026T020000
        TZOFFSETFROM:-0400
        TZOFFSETTO:-0500
        TZNAME:EST
        END:STANDARD
        BEGIN:DAYLIGHT
        DTSTART:19970406T020000
        RDATE:19970406T020000
        TZOFFSETFROM:-0500
        TZOFFSETTO:-0400
        TZNAME:EDT
        END:DAYLIGHT
        END:VTIMEZONE

   Figure 25
   Example 2: Current
      globally defined time zone rules registry (when such registry is
      defined).

         Note: This document does not define a naming convention for
         time zone identifiers.  Implementers may want to use the Eastern United States
   using a RRULE recurrence pattern.  Note that there naming
         conventions defined in existing time zone specifications such
         as the public-domain Olson database [TZDB].  The specification
         of globally unique time zone identifiers is no effective
   end date not addressed by
         this document and is left for future study.

      The following are examples of this property parameter:

          DTSTART;TZID=US-Eastern:19980119T020000

          DTEND;TZID=US-Eastern:19980119T030000

      The TZID property parameter MUST NOT be applied to either DATE-TIME or
      TIME properties whose time values are specified in UTC.

      The use of the Standard Time local time in a DATE-TIME or Daylight Time rules.  This
   information would TIME value without the
      TZID property parameter is to be valid for interpreted as a recurring event starting today and
   continuing indefinitely.

        BEGIN:VTIMEZONE
        TZID:US-Eastern
        LAST-MODIFIED:19870101T000000Z
        TZURL:http://zones.stds_r_us.net/tz/US-Eastern
        BEGIN:STANDARD
        DTSTART:19671029T020000
        RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
        TZOFFSETFROM:-0400
        TZOFFSETTO:-0500
        TZNAME:EST
        END:STANDARD
        BEGIN:DAYLIGHT
        DTSTART:19870405T020000
        RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
        TZOFFSETFROM:-0500
        TZOFFSETTO:-0400
        TZNAME:EDT
        END:DAYLIGHT
        END:VTIMEZONE

   Figure 26
   Example 3: A fictitious set local time
      value, regardless of rules for the Eastern United States,
   where the Daylight Time rule has an effective end date (i.e., after
   that date, Daylight Time is no longer observed).

        BEGIN:VTIMEZONE
        TZID:US- -Fictitious-Eastern
        LAST-MODIFIED:19870101T000000Z
        BEGIN:STANDARD
        DTSTART:19671029T020000
        RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
        TZOFFSETFROM:-0400
        TZOFFSETTO:-0500
        TZNAME:EST
        END:STANDARD
        BEGIN:DAYLIGHT
        DTSTART:19870405T020000
        RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4;UNTIL=19980404T070000Z
        TZOFFSETFROM:-0500
        TZOFFSETTO:-0400
        TZNAME:EDT
        END:DAYLIGHT
        END:VTIMEZONE

   Figure 27
   Example 4: A fictitious set existence of rules for "VTIMEZONE" calendar
      components in the Eastern United States,
   where iCalendar object.

      For more information see the first Daylight Time rule has an effective end date.  There
   is a second Daylight Time rule that picks up where sections on the other left
   off.

        BEGIN:VTIMEZONE
        TZID:US- -Fictitious-Eastern
        LAST-MODIFIED:19870101T000000Z
        BEGIN:STANDARD
        DTSTART:19671029T020000
        RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
        TZOFFSETFROM:-0400
        TZOFFSETTO:-0500
        TZNAME:EST
        END:STANDARD
        BEGIN:DAYLIGHT
        DTSTART:19870405T020000
        RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4;UNTIL=19980404T070000Z
        TZOFFSETFROM:-0500
        TZOFFSETTO:-0400
        TZNAME:EDT
        END:DAYLIGHT
        BEGIN:DAYLIGHT
        DTSTART:19990424T020000
        RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=4
        TZOFFSETFROM:-0500
        TZOFFSETTO:-0400
        TZNAME:EDT
        END:DAYLIGHT
        END:VTIMEZONE

   Figure 28

7.6.  Alarm Component

   Component data types DATE-TIME
      and TIME.

3.2.20.  Value Data Types

   Parameter Name: VALARM VALUE

   Purpose: Provide To explicitly specify the data type format for a grouping of component properties that define an
   alarm.

   Formal property
      value.

   Format Definition: A "VALARM" calendar component The property parameter is defined by the following
      notation:

             alarmc

          valuetypeparam = "BEGIN" ":" "VALARM" CRLF
                          (audioprop "VALUE" "=" valuetype

          valuetype  = ("BINARY"
                     / dispprop "BOOLEAN"
                     / emailprop "CAL-ADDRESS"
                     / procprop)
                          "END" ":" "VALARM" CRLF

        audioprop  = 2*(
                   ; 'action' and 'trigger' are both REQUIRED,
                   ; but MUST NOT occur more than once

                   action / trigger /

                   ; 'duration' and 'repeat' are both optional,
                   ; and MUST NOT occur more than once each,
                   ; but if one occurs, so MUST the other

                   duration "DATE"
                     / repeat "DATE-TIME"
                     /

                   ; the following is optional,
                   ; but MUST NOT occur more than once

                   attach "DURATION"
                     /

                   ; the following is optional,
                   ; and MAY occur more than once

                   x-prop

                   )

        dispprop   = 3*(

                   ; the following are all REQUIRED,
                   ; but MUST NOT occur more than once

                   action "FLOAT"
                     / description "INTEGER"
                     / trigger "PERIOD"
                     /

                   ; 'duration' and 'repeat' are both optional,
                   ; and MUST NOT occur more than once each,
                   ; but if one occurs, so MUST the other

                   duration "RECUR"
                     / repeat "TEXT"
                     /

                   ; the following is optional,

                   ; and MAY occur more than once

                   *x-prop

                   )
        emailprop  = 5*(

                   ; the following are all REQUIRED,
                   ; but MUST NOT occur more than once

                   action "TIME"
                     / description "URI"
                     / trigger "UTC-OFFSET"
                     / summary

                   ; the following is REQUIRED, x-name
                     ; and MAY occur more than once

                   attendee Some experimental iCalendar data type.
                     / iana-token)
                     ; 'duration' and 'repeat' are both optional,
                   ; and MUST NOT occur more than once each,
                   ; but if one occurs, so MUST the Some other

                   duration / repeat /

                   ; the following are optional,
                   ; and MAY occur more than once

                   attach / x-prop

                   )

        procprop   = 3*(

                   ; IANA registered iCalendar data type.

   Description: The parameter specifies the following are all REQUIRED,
                   ; but MUST NOT occur more than once

                   action / attach / trigger /

                   ; 'duration' and 'repeat' are both optional,
                   ; data type and MUST NOT occur more than once each,
                   ; but if one occurs, so MUST format of the other

                   duration / repeat /

                   ; 'description' is optional,
                   ; and
      property value.  The property values MUST NOT occur more than once

                   description /

                   ; the following is optional,
                   ; and MAY occur more than once
                   x-prop

                   )

   Figure 29

   Description: A "VALARM" calendar component is a grouping be of component
   properties that is a reminder or alarm for an event or a to-do. single value
      type.  For example, it may be used to define a reminder for a pending event or
   an overdue to-do.

   The "VALARM" calendar component MUST include the "ACTION" and
   "TRIGGER" properties.  The "ACTION" "RDATE" property further constrains the
   "VALARM" calendar component in the following ways:

   When the action is "AUDIO", the alarm can also include one and only
   one "ATTACH" property, which MUST point to cannot have a sound resource, which is
   rendered when the alarm is triggered.

   When combination
      of DATE- TIME and TIME value types.

      If the action property's value is "DISPLAY", the alarm MUST also include a
   "DESCRIPTION" property, which contains the text to default value type, then this
      parameter need not be displayed when
   the alarm is triggered.

   When specified.  However, if the action property's
      default value type is "EMAIL", the alarm overridden by some other allowable value
      type, then this parameter MUST include a "DESCRIPTION"
   property, which contains the text to be used as the message body, a
   "SUMMARY" property, which contains specified.

3.3.  Property Value Data Types

   The properties in an iCalendar object are strongly typed.  The
   definition of each property restricts the text value to be used as the message
   subject, and one or more "ATTENDEE" properties, which contain the
   email address of attendees to receive the message.  It can also
   include one
   value data types, or more "ATTACH" properties, which are intended to be
   sent as message attachments.  When the alarm is triggered, the email
   message is sent.

   When the action is "PROCEDURE", the alarm MUST include one and only
   one "ATTACH" property, which MUST point to a procedure resource,
   which is invoked when the alarm is triggered. simply value types, defined in this section.
   The "VALARM" calendar component MUST only appear within either a
   "VEVENT" or "VTODO" calendar component.  "VALARM" calendar components
   cannot be nested.  Multiple mutually independent "VALARM" calendar
   components can be specified value type for a single "VEVENT" or "VTODO" calendar
   component.

   The "TRIGGER" property specifies when the alarm will either be triggered.
   The "TRIGGER" property specifies a duration prior to specified implicitly as
   the start of an
   event default value type or a to-do.  The "TRIGGER" edge may will be explicitly set to be
   relative to the "START" or "END" of the event or to-do specified with the
   "RELATED" parameter of
   "VALUE" parameter.  If the "TRIGGER" property.  The "TRIGGER"
   property value type can alternatively be set to an absolute calendar
   date and time of day value.

   In an alarm set to trigger on the "START" of an event or to-do, the
   "DTSTART" property MUST be present in the associated event or to-do.
   In an alarm in a "VEVENT" calendar component set to trigger on the
   "END" property is one of the event, either the "DTEND" property
   alternate valid types, then it MUST be present, or explicitly specified with the "DTSTART" and "DURATION"
   "VALUE" parameter.

3.3.1.  Binary

   Value Name: BINARY

   Purpose: This value type is used to identify properties MUST both be present.  In an
   alarm in that contain
      a "VTODO" calendar component set to trigger on the "END" character encoding of
   the to-do, either the "DUE" property MUST be present, or the
   "DTSTART" and "DURATION" properties MUST both inline binary data.  For example, an
      inline attachment of an object code might be present. included in an
      iCalendar object.

   Format Definition: The alarm can be value type is defined such that it triggers repeatedly. by the following
      notation:

        binary     = *(4b-char) [b-end]
        ; A
   definition of an alarm "BASE64" encoded character string, as defined by [RFC2045].

        b-end      = (2b-char "==") / (3b-char "=")

        b-char = ALPHA / DIGIT / "+" / "/"

   Description: Property values with a repeating trigger this value type MUST also include both the
   "DURATION" and "REPEAT" properties.  The "DURATION" property
   specifies the delay period, after which the alarm will repeat.  The
   "REPEAT" property specifies the number of additional repetitions that
   the alarm will triggered.  This repitition count is in addition to
      the initial triggering of the alarm.  Both inline encoding parameter sequence of these properties ";ENCODING=BASE64".
      That is, all inline binary data MUST first be present character encoded
      using the "BASE64" encoding method defined in order to specify a repeating alarm.  If one of these
   two properties [RFC2045].  No
      additional content value encoding (i.e., BACKSLASH character
      encoding) is absent, then the alarm will not repeat beyond the
   initial trigger. defined for this value type.

   Example: The "ACTION" property following is used within the "VALARM" calendar component
   to specify the type of action invoked when the alarm is triggered.
   The "VALARM" properties provide enough information for a specific
   action to be invoked.  It is typically the responsibility an abridged example of a
   "Calendar User Agent" (CUA) to deliver the alarm in the specified
   fashion.  An "ACTION" property "BASE64" encoded
      binary value data.

    ATTACH;VALUE=BINARY;ENCODING=BASE64:MIICajCCAdOgAwIBAgICBEUwDQY
     JKoZIhvcNAQEEBQAwdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlI
     ENvbW11bmljYXRpb25zIENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZv
       <...remainder of AUDIO specifies an alarm that
   causes a sound to be played "BASE64" encoded binary data...>

3.3.2.  Boolean

   Value Name: BOOLEAN

   Purpose: This value type is used to alert the user; DISPLAY specifies an
   alarm identify properties that causes contain
      either a text message to be displayed to the user; EMAIL
   specifies an alarm that causes an electronic email message to be
   delivered to one "TRUE" or more email addresses; and PROCEDURE specifies an
   alarm that causes a procedure to be executed. "FALSE" Boolean value.

   Format Definition: The "ACTION" property
   MUST specify one and only one of these values.

   In an AUDIO alarm, if value type is defined by the optional "ATTACH" property following
      notation:

        boolean    = "TRUE" / "FALSE"

   Description: These values are case insensitive text.  No additional
      content value encoding (i.e., BACKSLASH character encoding) is included, it
   MUST specify an audio sound resource.
      defined for this value type.

   Example: The intention following is that the
   sound will be played as the alarm effect.  If an "ATTACH" example of a hypothetical property is
   specified that does not refer
      has a BOOLEAN value type:

      GIBBERISH:TRUE

3.3.3.  Calendar User Address

   Value Name: CAL-ADDRESS

   Purpose: This value type is used to identify properties that contain
      a sound resource, or if the
   specified sound resource cannot be rendered (because its format calendar user address.

   Format Definition: The value type is
   unsupported, or because it cannot be retrieved), then the CUA or
   other entity responsible for playing defined by the sound may choose following
      notation:

        cal-address        = uri

   Description: The value is a fallback
   action, such URI as playing a built-in default sound, defined by [RFC1738] or playing no sound
   at all.

   In any other
      IANA registered form for a DISPLAY alarm, the intended alarm effect is URI.  When used to address an Internet
      email transport address for a calendar user, the text value
   of the "DESCRIPTION" property to MUST be displayed to the user.

   In an EMAIL alarm, the intended alarm effect a
      MAILTO URI, as defined by [RFC1738].  No additional content value
      encoding (i.e., BACKSLASH character encoding) is defined for an email message
   to be composed and delivered this
      value type.

   Example:

        ATTENDEE:MAILTO:jane_doe@host.com

3.3.4.  Date

   Value Name: DATE

   Purpose: This value type is used to all the addresses specified identify values that contain a
      calendar date.

   Format Definition: The value type is defined by the
   "ATTENDEE" properties in following
      notation:

        date               = date-value

        date-value         = date-fullyear date-month date-mday
        date-fullyear      = 4DIGIT
        date-month         = 2DIGIT        ;01-12
        date-mday          = 2DIGIT        ;01-28, 01-29, 01-30, 01-31
                                           ;based on month/year

   Description: If the "VALARM" calendar component.  The
   "DESCRIPTION" property permits, multiple "date" values are
      specified as a COMMA character (US-ASCII decimal 44) separated
      list of values.  The format for the "VALARM" calendar component MUST be
   used value type is expressed as the body text of the message,
      [ISO.8601.1988] complete representation, basic format for a
      calendar date.  The textual format specifies a four-digit year,
      two-digit month, and two-digit day of the "SUMMARY" property MUST
   be used as month.  There are no
      separator characters between the subject year, month and day component
      text.  Any "ATTACH" properties in the "VALARM"
   calendar component SHOULD be sent as attachments

      No additional content value encoding (i.e., BACKSLASH character
      encoding) is defined for this value type.

   Example: The following represents July 14, 1997:

        19970714

3.3.5.  Date-Time

   Value Name: DATE-TIME

   Purpose: This value type is used to the message.

   In a PROCEDURE alarm, the "ATTACH" property in the "VALARM" calendar
   component MUST identify values that specify a procedure or program that
      precise calendar date and time of day.

   Format Definition: The value type is intended to be
   invoked as the alarm effect.  If defined by the procedure or program is following
      notation:

        date-time  = date "T" time ;As specified in a
   format that cannot be rendered, then no procedure alarm will be
   invoked. the date and time
                                   ;value definitions
   Description: If the "DESCRIPTION" property permits, multiple "date-time" values are
      specified as a COMMA character (US-ASCII decimal 44) separated
      list of values.  No additional content value encoding (i.e.,
      BACKSLASH character encoding) is present, its defined for this value
   specifies the argument string to be passed type.

      The "DATE-TIME" data type is used to the procedure or
   program.  "Calendar User Agents" identify values that receive an iCalendar object
   with this category of alarm, can disable or allow the "Calendar User"
   to disable, or otherwise ignore this type of alarm.  While contain
      a very
   useful alarm capability, the PROCEDURE type precise calendar date and time of alarm SHOULD be
   treated by day.  The format is based on
      the "Calendar User Agent" as [ISO.8601.1988] complete representation, basic format for a potential security risk.

   Example 1: A "VALARM"
      calendar component that specifies an audio
   alarm that will sound at a precise time date and repeat 4 more times at 15
   minute intervals.

        BEGIN:VALARM
        TRIGGER;VALUE=DATE-TIME:19970317T133000Z
        REPEAT:4
        DURATION:PT15M
        ACTION:AUDIO
        ATTACH;FMTTYPE=audio/basic:ftp://host.com/pub/sounds/bell-01.aud
        END:VALARM

   Figure 30

   Example 2: A "VALARM" calendar component that specifies time of day.  The text format is a display
   alarm that will trigger 30 minutes before the scheduled start concatenation
      of the
   event or "date", followed by the due date/time of LATIN CAPITAL LETTER T character
      (US-ASCII decimal 84) time designator, followed by the to-do it is associated with "time"
      format.

      The "DATE-TIME" data type expresses time values in three forms:

      The form of date and
   will repeat 2 more times at 15 minute intervals:

        BEGIN:VALARM
        TRIGGER:-PT30M
        REPEAT:2
        DURATION:PT15M
        ACTION:DISPLAY
        DESCRIPTION:Breakfast meeting time with executive\n
         team at 8:30 AM EST.
        END:VALARM
   Figure 31

   Example 3: A "VALARM" calendar component that specifies an email
   alarm that will trigger 2 days before UTC offset MUST NOT be used.  For
      example, the scheduled due date/time of following is not valid for a to-do it date-time value:

              DTSTART:19980119T230000-0800       ;Invalid time format

      FORM #1: DATE WITH LOCAL TIME

      The date with local time form is associated with.  It simply a date-time value that
      does not repeat.  The email has contain the UTC designator nor does it reference a
   subject, body and attachment link.

        BEGIN:VALARM
        TRIGGER:-P2D
        ACTION:EMAIL
        ATTENDEE:MAILTO:john_doe@host.com
        SUMMARY:*** REMINDER: SEND AGENDA FOR WEEKLY STAFF MEETING ***
        DESCRIPTION:A draft agenda needs time
      zone.  For example, the following represents Janurary 18, 1998, at
      11 PM:

              DTSTART:19980118T230000

      Date-time values of this type are said to be sent out "floating" and are
      not bound to the attendees any time zone in particular.  They are used to
      represent the weekly managers meeting (MGR-LIST). Attached same hour, minute, and second value regardless of
      which time zone is a
          pointer the document template for the agenda file.
        ATTACH;FMTTYPE=application/msword:http://host.com/templates/agen
         da.doc
        END:VALARM

   Figure 32

   Example 4: A "VALARM" calendar component currently being observed.  For example, an
      event can be defined that specifies a procedural
   alarm indicates that will trigger at a precise date/time and will repeat 23
   more times at one hour intervals.  The alarm will invoke a procedure
   file.

        BEGIN:VALARM
        TRIGGER;VALUE=DATE-TIME:19980101T050000Z
        REPEAT:23
        DURATION:PT1H
        ACTION:PROCEDURE
        ATTACH;FMTTYPE=application/octet-stream:ftp://host.com/novo-
         procs/felizano.exe
        END:VALARM

   Figure 33

8.  Properties

   A property is the definition of an individual attribute describing a
   calendar or a calendar component.  A property takes the form defined
   by will be
      busy from 11:00 AM to 1:00 PM every day, no matter which time zone
      the "contentline" notation defined in section 4.1.1.

   The following person is an example of in.  In these cases, a property:

        DTSTART:19960415T133000Z

   This memo imposes no ordering local time can be specified.
      The recipient of properties within an iCalendar
   object.

   Property names, parameter names and enumerated parameter values are
   case insensitive.  For example, the object with a property name "DUE" is value
      consisting of a local time, without any relative time zone
      information, SHOULD interpret the same value as "due" and "Due", DTSTART;TZID=US-Eastern:19980714T120000 is being fixed to whatever
      time zone the
   same as DtStart;TzID=US-Eastern:19980714T120000.

8.1.  Calendar Properties

   The Calendar Properties are attributes ATTENDEE is in at any given moment.  This means that apply to
      two ATTENDEEs, in different time zones, receiving the iCalendar
   object, same event
      definition as a whole.  These properties do not appear within a calendar
   component.  They SHOULD floating time, may be specified after the "BEGIN:VCALENDAR"
   property and prior to any calendar component.

8.1.1.  Calendar Scale

   Property Name: CALSCALE

   Purpose: This property defines participating in the calendar scale event
      at different actual times.  Floating time SHOULD only be used for
      where that is the
   calendar information specified reasonable behavior.

      In most cases, a fixed time is desired.  To properly communicate a
      fixed time in the iCalendar object.

   Value Type: TEXT

   do Property Parameters: Non-standard a property parameters can be
   specified on this property.

   Conformance: Property can value, either UTC time or local time with
      time zone reference MUST be specified in an iCalendar object. specified.

      The
   default use of local time in a DATE-TIME value is "GREGORIAN".

   Description: This memo is based on without the Gregorian calendar scale.  The
   Gregorian calendar scale is assumed if this TZID
      property parameter is not specified to be interpreted as floating time,
      regardless of the existence of "VTIMEZONE" calendar components in
      the iCalendar object.  It is expected that other calendar scales
   will be defined in other specifications or by future versions of this
   memo.

   Formal Definition:

      FORM #2: DATE WITH UTC TIME

      The property date with UTC time, or absolute time, is defined identified by a LATIN
      CAPITAL LETTER Z suffix character (US-ASCII decimal 90), the following notation:

        calscale   = "CALSCALE" calparam ":" calvalue CRLF

        calparam   = *(";" xparam)

        calvalue   = "GREGORIAN" / iana-token

   Figure 35

   Example: The following is an example of this property:

        CALSCALE:GREGORIAN

   Figure 36

8.1.2.  Method

   Property Name: METHOD

   Purpose: This property defines UTC
      designator, appended to the iCalendar object method associated
   with time value.  For example, the calendar object.

   Value Type: TEXT

   Property Parameters: Non-standard property parameters can be
   specified on this property.

   Conformance:
      following represents January 19, 1998, at 0700 UTC:

              DTSTART:19980119T070000Z

      The TZID property can parameter MUST NOT be applied to DATE-TIME
      properties whose time values are specified in an iCalendar object.

   Description: When used in a MIME message entity, the value of this
   property MUST be the same as the Content-Type "method" parameter
   value.  This property can only appear once within UTC.

      FORM #3: DATE WITH LOCAL TIME AND TIME ZONE REFERENCE

      The date and local time with reference to time zone information is
      identified by the iCalendar
   object.  If either use the "METHOD" TZID property or the Content-Type "method" parameter is specified, then to reference the other MUST also be specified.

   No methods are defined by this specification.  This
      appropriate time zone definition.  TZID is discussed in detail in
      the subject of
   other specifications, such as section on Time Zone.  For example, the iCalendar Transport-independent
   Interoperability Protocol (iTIP) defined by [ITIP].

   If this property is not present following represents 2
      AM in New York on Janurary 19, 1998:

             DTSTART;TZID=US-Eastern:19980119T020000

   Example: The following represents July 14, 1997, at 1:30 PM in New
      York City in each of the iCalendar object, then a
   scheduling transaction three time formats, using the "DTSTART"
      property.

        DTSTART:19970714T133000            ;Local time
        DTSTART:19970714T173000Z           ;UTC time
        DTSTART;TZID=US-Eastern:19970714T133000    ;Local time and time
                           ; zone reference

      A time value MUST NOT be assumed.  In such cases, ONLY specify 60 seconds when specifying the
   iCalendar object
      periodic "leap second" in the time value.  For example:

        COMPLETED:19970630T235960Z

3.3.6.  Duration

   Value Name: DURATION

   Purpose: This value type is merely being used to transport identify properties that contain
      a snapshot of some
   calendar information; without the intention duration of conveying a scheduling
   semantic.

   Formal time.

   Format Definition: The property value type is defined by the following
      notation:

        method

        dur-value  = "METHOD" metparam ":" metvalue CRLF

        metparam (["+"] / "-") "P" (dur-date / dur-time / dur-week)

        dur-date   = *(";" xparam)

        metvalue dur-day [dur-time]
        dur-time   = iana-token

   Example: The following is "T" (dur-hour / dur-minute / dur-second)
        dur-week   = 1*DIGIT "W"
        dur-hour   = 1*DIGIT "H" [dur-minute]
        dur-minute = 1*DIGIT "M" [dur-second]
        dur-second = 1*DIGIT "S"
        dur-day    = 1*DIGIT "D"

   Description: If the property permits, multiple "duration" values are
      specified by a hypothetical example COMMA character (US-ASCII decimal 44) separated
      list of this property to
   convey that the iCalendar object values.  The format is a request for a meeting:

        METHOD:REQUEST

   Figure 38

8.1.3.  Product Identifier

   Property Name: PRODID

   Purpose: This property specifies expressed as the identifier [ISO.8601.1988]
      basic format for the product that
   created the iCalendar object.

   Value Type: TEXT

   Property Parameters: Non-standard property parameters can be
   specified on this property.

   Conformance: duration of time.  The property MUST be specified once format can represent
      durations in an iCalendar
   object.

   Description: The vendor terms of the implementation SHOULD assure that this
   is a globally unique identifier; using some technique such as an FPI
   value, as weeks, days, hours, minutes, and seconds.

      No additional content value encoding (i.e., BACKSLASH character
      encoding) are defined in [ISO 9070].

   This property SHOULD not be used to alter the interpretation of an
   iCalendar object beyond the semantics specified in for this memo.  For
   example, it value type.

   Example: A duration of 15 days, 5 hours and 20 seconds would be:

        P15DT5H0M20S

      A duration of 7 weeks would be:

        P7W

3.3.7.  Float

   Value Name: FLOAT

   Purpose: This value type is not to be used to further the understanding of non-
   standard properties.

   Formal identify properties that contain
      a real number value.

   Format Definition: The property value type is defined by the following
      notation:

        prodid     = "PRODID" pidparam ":" pidvalue CRLF
        pidparam   = *(";" xparam)

        pidvalue

        float      = text
        ;Any text that describes (["+"] / "-") 1*DIGIT ["." 1*DIGIT]
   Description: If the product and version
        ;and that is generally assured property permits, multiple "float" values are
      specified by a COMMA character (US-ASCII decimal 44) separated
      list of being unique.

   Figure 39

   Example: The following values.

      No additional content value encoding (i.e., BACKSLASH character
      encoding) is an example of defined for this property.  It does not
   imply that English is the default language.

        PRODID:-//ABC Corporation//NONSGML My Product//EN

   Figure 40

8.1.4.  Version

   Property value type.

   Example:

        1000000.0000001
        1.333
        -3.14

3.3.8.  Integer

   Value Name: VERSION INTEGER

   Purpose: This property specifies the identifier corresponding to the
   highest version number or the minimum and maximum range of the
   iCalendar specification that is required in order to interpret the
   iCalendar object.

   Value Type: TEXT

   Property Parameters: Non-standard property parameters can be
   specified on this property.

   Conformance: This property MUST be specified by an iCalendar object,
   but MUST only be specified once.

   Description: A value of "2.0" corresponds type is used to this memo.

   Formal identify properties that contain
      a signed integer value.

   Format Definition: The property value type is defined by the following
      notation:

        version    = "VERSION" verparam ":" vervalue CRLF

        verparam   = *(";" xparam)

        vervalue

        integer    = "2.0"         ;This memo
                   / maxver (["+"] / (minver ";" maxver)

        minver     = [A IANA registered iCalendar version identifier]
        ;Minimum iCalendar version needed to parse the iCalendar object

        maxver     = [A IANA registered iCalendar version identifier]
        ;Maximum iCalendar version needed to parse "-") 1*DIGIT

   Description: If the iCalendar object

   Example: The following is an example of this property:

        VERSION:2.0

8.2.  Descriptive Component Properties

   The following properties can appear within calendar components, as property permits, multiple "integer" values are
      specified by each component property definition.  These specify
   descriptive information about calendar components.

8.2.1.  Attachment

   Property Name: ATTACH

   Purpose: The property provides the capability to associate a document
   object with a calendar component.

   Value Type: COMMA character (US-ASCII decimal 44) separated
      list of values.  The default value type valid range for this property "integer" is URI.  The
   value type can also be set -2147483648 to BINARY
      2147483647.  If the sign is not specified, then the value is
      assumed to indicate inline binary
   encoded be positive.

      No additional content information.

   Property Parameters: Non-standard, inline encoding, format type and value data type property parameters can be specified on encoding (i.e., BACKSLASH character
      encoding) is defined for this
   property.

   Conformance: The property can be specified in a "VEVENT", "VTODO",
   "VJOURNAL" or "VALARM" calendar components.

   Description: The property can be specified within "VEVENT", "VTODO",
   "VJOURNAL", or "VALARM" calendar components. value type.

   Example:

        1234567890
        -1234567890
        +1234567890
        432109876

3.3.9.  Period of Time

   Value Name: PERIOD
   Purpose: This property can be
   specified multiple times within an iCalendar object. value type is used to identify values that contain a
      precise period of time.

   Format Definition: The property value type is defined by the following
      notation:

        attach

      period     = "ATTACH" attparam ":" uri  CRLF

        attach     =/ "ATTACH" attparam ";" "ENCODING" "=" "BASE64"
                      ";" "VALUE" "=" "BINARY" ":" binary

        attparam period-explicit / period-start

      period-explicit = *( date-time "/" date-time
      ; the following is optional, [ISO.8601.1988] complete representation basic format for a
      ; but period of time consisting of a start and end. The start MUST NOT occur more than once

                   (";" fmttypeparam) /
      ; be before the following is optional, end.

      period-start = date-time "/" dur-value
      ; and MAY occur more than once

                   (";" xparam)

                   )

   Example: The following are examples [ISO.8601.1988] complete representation basic format for a
      ; period of time consisting of this property:

        ATTACH:CID:jsmith.part3.960817T083000.xyzMail@host1.com

        ATTACH;FMTTYPE=application/postscript:ftp://xyzCorp.com/pub/
         reports/r-960812.ps

8.2.2.  Categories

   Property Name: CATEGORIES

   Purpose: This property defines the categories for a calendar
   component.

   Value Type: TEXT

   Property Parameters: Non-standard start and language property parameters
   can be specified on this property.

   Conformance: The property can be specified within "VEVENT", "VTODO"
   or "VJOURNAL" calendar components.

   Description: This property is used to specify categories or subtypes positive duration
      ; of time.

   Description: If the calendar component.  The categories property permits, multiple "period" values are useful in searching
   for a calendar component of a particular type and category.  Within
   the "VEVENT", "VTODO" or "VJOURNAL" calendar components, more than
   one category can be
      specified as a list of categories separated by
   the a COMMA character (US-ASCII decimal 44).

        categories = "CATEGORIES" catparam ":" text *("," text)
                     CRLF

        catparam   = *(

                   ; the following is optional,
                   ; but MUST NOT occur more than once

                   (";" languageparam ) /

                   ; the following is optional,
                   ; and MAY occur more than once

                   (";" xparam)

                   )

   The following 44) separated
      list of values.  There are examples two forms of categories.

        CATEGORIES:APPOINTMENT,EDUCATION

        CATEGORIES:MEETING

8.2.3.  Classification

   Property Name: CLASS

   Purpose: This property defines the access classification for a
   calendar component.

   Value Type: TEXT

   Property Parameters: Non-standard property parameters can be
   specified on this property.

   Conformance: The property can be specified once in period of time.  First,
      a "VEVENT",
   "VTODO" or "VJOURNAL" calendar components.

   Description: An access classification period of time is only one component identified by its start and its end.  This
      format is expressed as the [ISO.8601.1988] complete
      representation, basic format for "DATE-TIME" start of the
   general security system within a calendar application.  It provides period,
      followed by a
   method of capturing SOLIDUS character (US-ASCII decimal 47), followed by
      the scope "DATE-TIME" of the access end of the calendar owner
   intends for information within an individual calendar entry. period.  The
   access classification start of an individual iCalendar component is useful
   when measured along with the other security components of a calendar
   system (e.g., calendar user authentication, authorization, access
   rights, access role, etc.).  Hence, period
      MUST be before the semantics end of the individual
   access classifications cannot period.  Second, a period of time
      can also be completely defined by this memo
   alone.  Additionally, due to the "blind" nature of most exchange
   processes using this memo, these access classifications cannot serve
   as an enforcement statement for a system receiving an iCalendar
   object.  Rather, they provide start and a method positive duration of time.
      The format is expressed as the [ISO.8601.1988] complete
      representation, basic format for capturing the intention "DATE-TIME" start of the calendar owner
      period, followed by a SOLIDUS character (US-ASCII decimal 47),
      followed by the [ISO.8601.1988] basic format for "DURATION" of the access
      period.

   Example: The period starting at 18:00:00 UTC, on January 1, 1997 and
      ending at 07:00:00 UTC on January 2, 1997 would be:

        19970101T180000Z/19970102T070000Z

      The period start at 18:00:00 on January 1, 1997 and lasting 5
      hours and 30 minutes would be:

        19970101T180000Z/PT5H30M

      No additional content value encoding (i.e., BACKSLASH character
      encoding) is defined for this value type.

3.3.10.  Recurrence Rule

   Value Name: RECUR

   Purpose: This value type is used to the calendar component.

   Formal identify properties that contain
      a recurrence rule specification.

   Format Definition: The property value type is defined by the following
      notation:

        class      = "CLASS" classparam ":" classvalue CRLF

        classparam = *(";" xparam)

        classvalue

    recur      = "PUBLIC" / "PRIVATE" / "CONFIDENTIAL" / iana-token
                   / x-name
        ;Default is PUBLIC

   Example: The following is an example of this property:

        CLASS:PUBLIC

8.2.4.  Comment

   Property Name: COMMENT

   Purpose: This property specifies non-processing information intended
   to provide "FREQ"=freq *(

               ; either UNTIL or COUNT may appear in a comment to the calendar user.

   Value Type: TEXT

   Property Parameters: Non-standard, alternate text representation 'recur',
               ; but UNTIL and
   language property parameters can be specified on this property.

   Conformance: This property can be specified COUNT MUST NOT occur in "VEVENT", "VTODO",
   "VJOURNAL", "VTIMEZONE" or "VFREEBUSY" calendar components.

   Description: The property can be specified multiple times.

   Formal Definition: The property is defined by the following notation:

        comment    = "COMMENT" commparam ":" text CRLF

        commparam  = *( same 'recur'

               ( ";" "UNTIL" "=" enddate ) /
               ( ";" "COUNT" "=" 1*DIGIT ) /

               ; the following rest of these keywords are optional,
               ; but MUST NOT occur more than once

                   (";" altrepparam)

               ( ";" "INTERVAL" "=" 1*DIGIT )          / (";" languageparam)
               ( ";" "BYSECOND" "=" byseclist )        /

                   ; the following is optional,
                   ; and MAY occur more than once

                   (";" xparam)
               ( ";" "BYMINUTE" "=" byminlist )

   Example: The following is an example of this property:

        COMMENT:The meeting really needs        /
               ( ";" "BYHOUR" "=" byhrlist )           /
               ( ";" "BYDAY" "=" bywdaylist )          /
               ( ";" "BYMONTHDAY" "=" bymodaylist )    /
               ( ";" "BYYEARDAY" "=" byyrdaylist )     /
               ( ";" "BYWEEKNO" "=" bywknolist )       /
               ( ";" "BYMONTH" "=" bymolist )          /
               ( ";" "BYSETPOS" "=" bysplist )         /
               ( ";" "WKST" "=" weekday )              /
               ( ";" x-name "=" text )
               )

    freq       = "SECONDLY" / "MINUTELY" / "HOURLY" / "DAILY"
               / "WEEKLY" / "MONTHLY" / "YEARLY"

    enddate    = date
    enddate    =/ date-time            ;An UTC value

    byseclist  = seconds / ( seconds *("," seconds) )

    seconds    = 1DIGIT / 2DIGIT       ;0 to include both ourselves 59

    byminlist  = minutes / ( minutes *("," minutes) )

    minutes    = 1DIGIT / 2DIGIT       ;0 to 59
    byhrlist   = hour / ( hour *("," hour) )

    hour       = 1DIGIT / 2DIGIT       ;0 to 23

    bywdaylist = weekdaynum / ( weekdaynum *("," weekdaynum) )

    weekdaynum = [([plus] ordwk / minus ordwk)] weekday

    plus       = "+"

    minus      = "-"

    ordwk      = 1DIGIT / 2DIGIT       ;1 to 53

    weekday    = "SU" / "MO" / "TU" / "WE" / "TH" / "FR" / "SA"
    ;Corresponding to SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY,
    ;FRIDAY, SATURDAY and the customer. We can't hold this  meeting without them.
          As a matter SUNDAY days of fact\, the venue for the meeting ought week.

    bymodaylist = monthdaynum / ( monthdaynum *("," monthdaynum) )

    monthdaynum = ([plus] ordmoday) / (minus ordmoday)

    ordmoday   = 1DIGIT / 2DIGIT       ;1 to be at
          their site. - - John

8.2.5.  Description

   Property Name: DESCRIPTION

   Purpose: This 31

    byyrdaylist = yeardaynum / ( yeardaynum *("," yeardaynum) )

    yeardaynum = ([plus] ordyrday) / (minus ordyrday)

    ordyrday   = 1DIGIT / 2DIGIT / 3DIGIT      ;1 to 366

    bywknolist = weeknum / ( weeknum *("," weeknum) )

    weeknum    = ([plus] ordwk) / (minus ordwk)

    bymolist   = monthnum / ( monthnum *("," monthnum) )

    monthnum   = 1DIGIT / 2DIGIT       ;1 to 12

    bysplist   = setposday / ( setposday *("," setposday) )

    setposday  = yeardaynum

   Description: If the property provides permits, multiple "recur" values are
      specified by a more complete description COMMA character (US-ASCII decimal 44) separated
      list of the
   calendar component, than that provided values.  The value type is a structured value consisting
      of a list of one or more recurrence grammar parts.  Each rule part
      is defined by a NAME=VALUE pair.  The rule parts are separated
      from each other by the "SUMMARY" property.

   Value Type: TEXT

   Property Parameters: Non-standard, alternate text representation and
   language property parameters can be specified on this property.

   Conformance: SEMICOLON character (US-ASCII decimal 59).

      The property can rule parts are not ordered in any particular sequence.
      Individual rule parts MUST only be specified in the "VEVENT", "VTODO",
   "VJOURNAL" or "VALARM" calendar components. once.

      The property can FREQ rule part identifies the type of recurrence rule.  This
      rule part MUST be specified multiple times only within a "VJOURNAL" calendar component.

   Description: This property is used in the "VEVENT" and "VTODO" recurrence rule.  Valid values
      include SECONDLY, to
   capture lengthy textual decriptions associated with the activity.

   This property is used in the "VJOURNAL" calendar component specify repeating events based on an interval
      of a second or more; MINUTELY, to capture
   one more textual journal entries.

   This property is used in the "VALARM" calendar component specify repeating events based
      on an interval of a minute or more; HOURLY, to capture
   the display text for specify repeating
      events based on an interval of an hour or more; DAILY, to specify
      repeating events based on an interval of a DISPLAY category day or more; WEEKLY, to
      specify repeating events based on an interval of alarm, a week or more;
      MONTHLY, to capture the body
   text for specify repeating events based on an EMAIL category interval of alarm a
      month or more; and YEARLY, to capture the argument
   string for a PROCEDURE category specify repeating events based on an
      interval of alarm.

   Formal Definition: a year or more.

      The property is defined by the following notation:

        description        = "DESCRIPTION" descparam ":" text CRLF

        descparam  = *(

                   ; the following are optional,
                   ; but MUST NOT occur more than once

                   (";" altrepparam) / (";" languageparam) /

                   ; INTERVAL rule part contains a positive integer representing
      how often the following is optional,
                   ; and MAY occur more than once

                   (";" xparam)

                   )

   Example: recurrence rule repeats.  The following default value is "1",
      meaning every second for a SECONDLY rule, or every minute for a
      MINUTELY rule, every hour for an example of the property with formatted
   line breaks in the property value:

        DESCRIPTION:Meeting to provide technical review HOURLY rule, every day for "Phoenix"
          design.\n Happy Face Conference Room. Phoenix design team
          MUST attend this meeting.\n RSVP to team leader. a
      DAILY rule, every week for a WEEKLY rule, every month for a
      MONTHLY rule and every year for a YEARLY rule.

      The following is an example of UNTIL rule part defines a date-time value which bounds the property with folding of long
   lines:

        DESCRIPTION:Last draft of
      recurrence rule in an inclusive manner.  If the new novel value specified by
      UNTIL is to be completed
          for synchronized with the editor's proof today.

8.2.6.  Geographic Position

   Property Name: GEO

   Purpose: This property specifies information related to specified recurrence, this date or
      date-time becomes the global
   position for last instance of the activity recurrence.  If
      specified by as a calendar component.

   Value Type: FLOAT.  The value date-time value, then it MUST be two SEMICOLON separated FLOAT
   values.

   Property Parameters: Non-standard property parameters can be
   specified on this property.

   Conformance: This property can be specified in "VEVENT" or "VTODO"
   calendar components.

   Description: The property value specifies latitude an
      UTC time format.  If not present, and longitude, in
   that order (i.e., "LAT LON" ordering).  The longitude represents the
   location east or west of COUNT rule part is also
      not present, the prime meridian as a positive or negative
   real number, respectively.  The longitude and latitude values MAY be
   specified up RRULE is considered to six decimal places, repeat forever.

      The COUNT rule part defines the number of occurrences at which will allow for accuracy to
   within one meter of geographical position.  Receiving applications
   MUST accept values of this precision and MAY truncate values of
   greater precision.

   Values for latitude and longitude shall be expressed
      range-bound the recurrence.  The "DTSTART" property value, if
      specified, counts as decimal
   fractions of degrees.  Whole degrees of latitude shall be represented
   by the first occurrence.

      The BYSECOND rule part specifies a two-digit COMMA character (US-ASCII
      decimal number ranging from 0 through 90.  Whole
   degrees 44) separated list of longitude shall be represented by seconds within a decimal number ranging
   from minute.  Valid
      values are 0 through 180.  When to 59.  The BYMINUTE rule part specifies a COMMA
      character (US-ASCII decimal fraction 44) separated list of minutes within
      an hour.  Valid values are 0 to 59.  The BYHOUR rule part
      specifies a degree is
   specified, it shall be COMMA character (US- ASCII decimal 44) separated from the whole number list
      of degrees by hours of the day.  Valid values are 0 to 23.

      The BYDAY rule part specifies a COMMA character (US-ASCII decimal point.

   Latitudes north
      44) separated list of days of the equator shall week; MO indicates Monday; TU
      indicates Tuesday; WE indicates Wednesday; TH indicates Thursday;
      FR indicates Friday; SA indicates Saturday; SU indicates Sunday.

      Each BYDAY value can also be specified preceded by a plus sign (+), positive (+n) or by
      negative (-n) integer.  If present, this indicates the absence nth
      occurrence of a minus sign (-), preceding the digits
   designating degrees.  Latitudes south of specific day within the Equator shall be
   designated by MONTHLY or YEARLY RRULE.
      For example, within a minus sign (-) preceding MONTHLY rule, +1MO (or simply 1MO)
      represents the digits designating
   degrees.  A point on first Monday within the Equator shall be assigned to month, whereas -1MO
      represents the Northern
   Hemisphere.

   Longitudes east last Monday of the prime meridian shall be month.  If an integer modifier
      is not present, it means all days of this type within the
      specified by frequency.  For example, within a plus
   sign (+), or by MONTHLY rule, MO
      represents all Mondays within the absence of month.

      The BYMONTHDAY rule part specifies a minus sign (-), preceding the digits
   designating degrees.  Longitudes west COMMA character (ASCII
      decimal 44) separated list of days of the meridian shall be
   designated by minus sign (-) preceding the digits designating
   degrees.  A point on the prime meridian shall be assigned month.  Valid values are
      1 to the
   Eastern Hemisphere.  A point on the 180th meridian shall be assigned 31 or -31 to -1.  For example, -10 represents the Western Hemisphere.  One exception tenth to this last convention is
   permitted.  For
      the special condition of describing a band last day of
   latitude around the earth, the East Bounding Coordinate data element
   shall be assigned the value +180 (180) degrees.

   Any spatial address with month.

      The BYYEARDAY rule part specifies a latitude COMMA character (US-ASCII
      decimal 44) separated list of days of +90 (90) or -90 degrees will
   specify the position at the North year.  Valid values are
      1 to 366 or South Pole, respectively.  The
   component for longitude may have any legal value.

   With -366 to -1.  For example, -1 represents the exception last day
      of the special condition described above, this
   form is specified in Department of Commerce, 1986, Representation of
   geographic point locations for information interchange (Federal
   Information Processing Standard 70-1): Washington, Department of
   Commerce, National Institute of Standards year (December 31st) and Technology. -306 represents the 306th to the
      last day of the year (March 1st).

      The simple formula for converting degrees-minutes-seconds into
   decimal degrees is: BYWEEKNO rule part specifies a COMMA character (US-ASCII
      decimal = degrees + minutes/60 + seconds/3600.

   Formal Definition: The property 44) separated list of ordinals specifying weeks of the
      year.  Valid values are 1 to 53 or -53 to -1.  This corresponds to
      weeks according to week numbering as defined in [ISO.8601.1988].
      A week is defined by as a seven day period, starting on the following notation:

        geo        = "GEO" geoparam ":" geovalue CRLF

        geoparam   = *(";" xparam)

        geovalue   = float ";" float
        ;Latitude and Longitude components

   Example: The following is an example day of this property:

        GEO:37.386013;-122.082932

8.2.7.  Location

   Property Name: LOCATION

   Purpose: The property defines the intended venue for
      the activity week defined by a calendar component.

   Value Type: TEXT

   Property Parameters: Non-standard, alternate text representation and
   language property parameters can be specified on this property.

   Conformance: This property can to be specified in "VEVENT" or "VTODO" the week start (see WKST).  Week number one
      of the calendar component.

   Description: Specific venues such as conference or meeting rooms may
   be explicitly specified using this property.  An alternate
   representation may be specified that year is a URI that points to
   directory information with more structured specification of the
   location. first week which contains at least
      four (4) days in that calendar year.  This rule part is only valid
      for YEARLY rules.  For example, 3 represents the alternate representation may specify
   either an LDAP URI pointing to an LDAP server entry or third week of the
      year.

         Note: Assuming a CID URI
   pointing to Monday week start, week 53 can only occur when
         Thursday is January 1 or if it is a MIME body leap year and Wednesday is
         January 1.

      The BYMONTH rule part containing specifies a vCard [RFC 2426] for COMMA character (US-ASCII
      decimal 44) separated list of months of the
   location.

   Format Definition: year.  Valid values
      are 1 to 12.

      The property is defined by WKST rule part specifies the following notation:

        location   = "LOCATION locparam ":" text CRLF

        locparam   = *(

                   ; day on which the following workweek starts.
      Valid values are optional,
                   ; but MUST NOT occur more than once

                   (";" altrepparam) / (";" languageparam) /

                   ; the following is optional,
                   ; MO, TU, WE, TH, FR, SA and MAY occur more SU.  This is
      significant when a WEEKLY RRULE has an interval greater than once

                   (";" xparam)

                   )

   Example: The following are some examples of this property:

        LOCATION:Conference Room - F123, Bldg. 002

        LOCATION;ALTREP="http://xyzcorp.com/conf-rooms/f123.vcf":
         Conference Room - F123, Bldg. 002

8.2.8.  Percent Complete

   Property Name: PERCENT-COMPLETE

   Purpose: 1,
      and a BYDAY rule part is specified.  This property is used by an assignee or delegatee of also significant when
      in a to-do
   to convey the percent completion of YEARLY RRULE when a to-do BYWEEKNO rule part is specified.  The
      default value is MO.

      The BYSETPOS rule part specifies a COMMA character (US-ASCII
      decimal 44) separated list of values which corresponds to the Organizer.

   Value Type: INTEGER

   Property Parameters: Non-standard property parameters can be nth
      occurrence within the set of events specified on this property.

   Conformance: This property can by the rule.  Valid
      values are 1 to 366 or -366 to -1.  It MUST only be specified used in a "VTODO" calendar
   component.

   Description: The property
      conjunction with another BYxxx rule part.  For example "the last
      work day of the month" could be represented as:

              RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-1

      Each BYSETPOS value is can include a positive integer between zero
   and one hundred.  A value of "0" (+n) or negative (-n)
      integer.  If present, this indicates the to-do has not yet been
   started.  A value nth occurrence of "100" indicates that the to-do has been
   completed.  Integer
      specific occurrence within the set of events specified by the
      rule.

      If BYxxx rule part values are found which are beyond the available
      scope (ie, BYMONTHDAY=30 in February), they are simply ignored.

      Information, not contained in between indicate the percent partially
   complete.

   When a to-do is assigned rule, necessary to multiple individuals, determine the property value
   indicates
      various recurrence instance start time and dates are derived from
      the percent complete Start Time (DTSTART) entry attribute.  For example,
      "FREQ=YEARLY;BYMONTH=1" doesn't specify a specific day within the
      month or a time.  This information would be the same as what is
      specified for that portion DTSTART.

      BYxxx rule parts modify the recurrence in some manner.  BYxxx rule
      parts for a period of time which is the to-do assigned
   to same or greater than the assignee
      frequency generally reduce or delegatee. limit the number of occurrences of
      the recurrence generated.  For example, if a to-do "FREQ=DAILY;BYMONTH=1"
      reduces the number of recurrence instances from all days (if
      BYMONTH tag is assigned not present) to
   both individuals "A" and "B".  A reply from "A" with all days in January.  BYxxx rule
      parts for a percent
   complete of "70" indicates that "A" has completed 70% period of time less than the to-do
   assigned to them.  A reply from "B" with a percent complete frequency generally
      increase or expand the number of "50"
   indicates "B" has completed 50% occurrences of the to-do assigned to them.

   Format Definition: The property recurrence.
      For example, "FREQ=YEARLY;BYMONTH=1,2" increases the number of
      days within the yearly recurrence set from 1 (if BYMONTH tag is defined by
      not present) to 2.

      If multiple BYxxx rule parts are specified, then after evaluating
      the specified FREQ and INTERVAL rule parts, the BYxxx rule parts
      are applied to the current set of evaluated occurrences in the
      following notation:

        percent = "PERCENT-COMPLETE" pctparam ":" integer CRLF

        pctparam   = *(";" xparam)

   Example: The following order: BYMONTH, BYWEEKNO, BYYEARDAY, BYMONTHDAY, BYDAY,
      BYHOUR, BYMINUTE, BYSECOND and BYSETPOS; then COUNT and UNTIL are
      evaluated.

      Here is an example of this property evaluating multiple BYxxx rule parts.

          DTSTART;TZID=US-Eastern:19970105T083000
          RRULE:FREQ=YEARLY;INTERVAL=2;BYMONTH=1;BYDAY=SU;BYHOUR=8,9;
           BYMINUTE=30
      First, the "INTERVAL=2" would be applied to show 39%
   completion:

        PERCENT-COMPLETE:39

8.2.9.  Priority

   Property Name: PRIORITY

   Purpose: The property defines the relative priority for a calendar
   component.

   Value Type: INTEGER

   Property Parameters: Non-standard property parameters can "FREQ=YEARLY" to
      arrive at "every other year".  Then, "BYMONTH=1" would be
   specified on this property.

   Conformance: The property can applied
      to arrive at "every January, every other year".  Then, "BYDAY=SU"
      would be specified applied to arrive at "every Sunday in a "VEVENT" January, every
      other year".  Then, "BYHOUR=8,9" would be applied to arrive at
      "every Sunday in January at 8 AM and 9 AM, every other year".
      Then, "BYMINUTE=30" would be applied to arrive at "every Sunday in
      January at 8:30 AM and 9:30 AM, every other year".  Then, lacking
      information from RRULE, the second is derived from DTSTART, to end
      up in "every Sunday in January at 8:30:00 AM and 9:30:00 AM, every
      other year".  Similarly, if the BYMINUTE, BYHOUR, BYDAY,
      BYMONTHDAY or "VTODO"
   calendar component.

   Description: BYMONTH rule part were missing, the appropriate
      minute, hour, day or month would have been retrieved from the
      "DTSTART" property.

      No additional content value encoding (i.e., BACKSLASH character
      encoding) is defined for this value type.

   Example: The priority following is a rule which specifies 10 meetings which
      occur every other day:

              FREQ=DAILY;COUNT=10;INTERVAL=2

      There are other examples specified as an integer in the range
   zero to nine.  A "RRULE" specification.

3.3.11.  Text

   Value Name: TEXT

   Purpose: This value type is used to identify values that contain
      human readable text.

   Format Definition: The character sets supported by this revision of zero (US-ASCII decimal 48) specifies an
   undefined priority.  A
      iCalendar are UTF-8 and US-ASCII thereof.  The applicability to
      other character sets is for future work.  The value of one (US-ASCII decimal 49) type is
      defined by the
   highest priority.  A value following notation.

        text       = *(TSAFE-CHAR / ":" / DQUOTE / ESCAPED-CHAR)
        ; Folded according to description above

        ESCAPED-CHAR = "\\" / "\;" / "\," / "\N" / "\n")
           ; \\ encodes \, \N or \n encodes newline
           ; \; encodes ;, \, encodes ,

        TSAFE-CHAR = %x20-21 / %x23-2B / %x2D-39 / %x3C-5B
                     %x5D-7E / NON-US-ASCII
           ; Any character except CTLs not needed by the current
           ; character set, DQUOTE, ";", ":", "\", ","
         Note: Certain other character sets may require modification of two (US-ASCII decimal 50)
         the above definitions, but this is beyond the second
   highest priority.  Subsequent numbers specify a decreasing ordinal
   priority.  A value scope of nine (US-ASCII decimal 58) is this
         document.

   Description: If the lowest
   priority.

   A CUA with property permits, multiple "text" values are
      specified by a three-level priority scheme COMMA character (US-ASCII decimal 44) separated
      list of "HIGH", "MEDIUM" and
   "LOW" values.

      The language in which the text is mapped into this represented can be controlled by
      the "LANGUAGE" property such that parameter.

      An intentional formatted text line break MUST only be included in
      a "TEXT" property value in by representing the
   range line break with the
      character sequence of one BACKSLASH (US-ASCII decimal 49) to four 92), followed by
      a LATIN SMALL LETTER N (US-ASCII decimal 52)
   specifies "HIGH" priority.  A value of five 110) or a LATIN CAPITAL
      LETTER N (US-ASCII decimal 53) 78), that is
   the normal "\n" or "MEDIUM" priority.  A value in the range of six (US-
   ASCII decimal 54) to nine (US-ASCII decimal 58) is "LOW" priority.

   A CUA with a priority schema of "A1", "A2", "A3", "B1", "B2", ...,
   "C3" is mapped into this "\N".

      The "TEXT" property such values may also contain special characters
      that are used to signify delimiters, such as a property value COMMA character for
      lists of one values or a SEMICOLON character for structured values.
      In order to support the inclusion of these special characters in
      "TEXT" property values, they MUST be escaped with a BACKSLASH
      character.  A BACKSLASH character (US-ASCII decimal 49) specifies "A1", 92) in a
      "TEXT" property value of two (US-
   ASCII decimal 50) specifies "A2", MUST be escaped with another BACKSLASH
      character.  A COMMA character in a "TEXT" property value of three MUST be
      escaped with a BACKSLASH character (US-ASCII decimal 51) specifies "A3", and so forth up to 92).  A
      SEMICOLON character in a "TEXT" property value of 9 MUST be escaped
      with a BACKSLASH character (US-ASCII decimal 58) specifies "C3".

   Other integer values are reserved for future use.

   Within 92).  However, a "VEVENT" calendar component, this property specifies
      COLON character in a
   priority for the event.  This "TEXT" property may value SHALL NOT be useful when more than
   one event is scheduled for a given time period.

   Within a "VTODO" calendar component, this property specified escaped
      with a
   priority for the to-do. BACKSLASH character.

   Example: A multiple line value of:

        Project XYZ Final Review
        Conference Room - 3B
        Come Prepared.

      would be represented as:

        Project XYZ Final Review\nConference Room - 3B\nCome Prepared.

3.3.12.  Time

   Value Name: TIME
   Purpose: This property value type is useful in prioritizing
   multiple action items for used to identify values that contain a given
      time period. of day.

   Format Definition: The property data type is specified defined by the following
      notation:

        priority

    time               = "PRIORITY" prioparam ":" privalue CRLF
        ;Default is zero

        prioparam time-hour time-minute time-second [time-utc]

    time-hour          = *(";" xparam)

        privalue 2DIGIT        ;00-23
    time-minute        = integer       ;Must be in 2DIGIT        ;00-59
    time-second        = 2DIGIT        ;00-60
    ;The "60" value is used to account for "leap" seconds.

    time-utc   = "Z"

   Description: If the range [0..9]
           ; All other property permits, multiple "time" values are reserved
      specified by a COMMA character (US-ASCII decimal 44) separated
      list of values.  No additional content value encoding (i.e.,
      BACKSLASH character encoding) is defined for future use this value type.

      The following "TIME" data type is an example of used to identify values that contain a property with the highest priority:

        PRIORITY:1
      time of day.  The following format is an example of a property with based on the [ISO.8601.1988] complete
      representation, basic format for a next highest
   priority:

        PRIORITY:2

   Example: time of day.  The following is an example text format
      consists of a property with no priority.
   This is equivalent to not specifying two-digit 24-hour of the "PRIORITY" property:

        PRIORITY:0

8.2.10.  Resources

   Property Name: RESOURCES

   Purpose: This property defines day (i.e., values 0-23),
      two- digit minute in the equipment or resources anticipated
   for an activity specified by a calendar entity..

   Value Type: TEXT

   Property Parameters: Non-standard, alternate text representation hour (i.e., values 0-59), and
   language property parameters can be specified on this property.

   Conformance: This property can be specified two-digit
      seconds in "VEVENT" or "VTODO"
   calendar component.

   Description: the minute (i.e., values 0-60).  The property seconds value is an arbitrary text.  More than one
   resource can of
      60 MUST only to be specified as a list used to account for "leap" seconds.  Fractions
      of resources separated by the
   COMMA character (US-ASCII decimal 44).

   Format Definition: The property is defined a second are not supported by this format.

      In parallel to the following notation:

        resources  = "RESOURCES" resrcparam ":" text *("," text) CRLF

        resrcparam = *(

                   ; "DATE-TIME" definition above, the following are optional,
                   ; but "TIME" data
      type expresses time values in three forms:

      The form of time with UTC offset MUST NOT occur more than once

                   (";" altrepparam) / (";" languageparam) /

                   ; be used.  For example,
      the following is optional,
                   ; and MAY occur more than once

                   (";" xparam)

                   )

   Example: NOT VALID for a time value:

              230000-0800        ;Invalid time format

      FORM #1 LOCAL TIME

      The following local time form is an example simply a time value that does not contain
      the UTC designator nor does it reference a time zone.  For
      example, 11:00 PM:

              230000

      Time values of this property:

        RESOURCES:EASEL,PROJECTOR,VCR

        RESOURCES;LANGUAGE=fr:1 raton-laveur

8.2.11.  Free/Busy Time Type

   Parameter Name: FBTYPE

   Purpose: To specify the free or busy type are said to be "floating" and are not
      bound to any time type.

   Description: The parameter specifies zone in particular.  They are used to represent
      the free or busy time type.  The same hour, minute, and second value FREE indicates that the regardless of which time interval
      zone is free for scheduling.
   The value BUSY currently being observed.  For example, an event can be
      defined that indicates that the an individual will be busy from 11:00
      AM to 1:00 PM every day, no matter which time interval zone the person is busy because one
   or more events have been scheduled for that interval.
      in.  In these cases, a local time can be specified.  The recipient
      of an iCalendar object with a property value
   BUSY-UNAVAILABLE indicates that consisting of a local
      time, without any relative time zone information, SHOULD interpret
      the value as being fixed to whatever time interval zone the ATTENDEE is busy and in
      at any given moment.  This means that two ATTENDEEs may
      participate in the interval can not same event at different UTC times; floating
      time SHOULD only be scheduled.  The value BUSY-TENTATIVE
   indicates used where that the is reasonable behavior.

      In most cases, a fixed time interval is busy because one or more events
   have been tentatively scheduled for that interval.  If not specified
   on desired.  To properly communicate a
      fixed time in a property that allows this parameter, the default is BUSY.

   Format Definition: value, either UTC time or local time with
      time zone reference MUST be specified.

      The use of local time in a TIME value without the TZID property
      parameter is defined by to be interpreted as a local time value, regardless
      of the existence of "VTIMEZONE" calendar components in the following
   notation:

        fbtypeparam        = "FBTYPE" "=" ("FREE" / "BUSY"
                           / "BUSY-UNAVAILABLE" / "BUSY-TENTATIVE"
                           / x-name
           ; Some experimental iCalendar data type.
                           / iana-token)

           ; Some other IANA registered
      iCalendar data type.

   Example: The following object.

      FORM #2: UTC TIME

      UTC time, or absolute time, is an example of this parameter on identified by a FREEBUSY
   property.

        FREEBUSY;FBTYPE=BUSY:19980415T133000Z/19980415T170000Z

8.2.12.  Participation Status

   Parameter Name: PARTSTAT

   Purpose: To specify LATIN CAPITAL
      LETTER Z suffix character (US-ASCII decimal 90), the participation status for UTC
      designator, appended to the calendar user
   specified by time value.  For example, the property.

   Description: This
      following represents 07:00 AM UTC:

              070000Z

      The TZID property parameter can MUST NOT be specified on applied to TIME properties with a
   CAL-ADDRESS value type.  The parameter identifies the participation
   status for the calendar user
      whose time values are specified in UTC.

      FORM #3: LOCAL TIME AND TIME ZONE REFERENCE

      The local time with reference to time zone information form is
      identified by the use the TZID property value.  The parameter values differ depending to reference the
      appropriate time zone definition.  TZID is discussed in detail in
      the section on whether they are associated with
   a group scheduled "VEVENT", "VTODO" or "VJOURNAL". Time Zone.

   Example: The values MUST
   match one following represents 8:30 AM in New York in Winter, five
      hours behind UTC, in each of the values allowed for the given calendar component.  If
   not specified on a property that allows this parameter, three formats using the default "X-
      TIMEOFDAY" non-standard property:

        X-TIMEOFDAY:083000

        X-TIMEOFDAY:133000Z

        X-TIMEOFDAY;TZID=US-Eastern:083000

3.3.13.  URI

   Value Name: URI

   Purpose: This value type is NEEDS-ACTION. used to identify values that contain a
      uniform resource identifier (URI) type of reference to the
      property value.

   Format Definition: The property parameter data type is defined by the following
      notation:

        partstatparam

        uri        = "PARTSTAT" "="
                            ("NEEDS-ACTION"        ; Event needs action
                           / "ACCEPTED"            ; Event accepted
                           / "DECLINED"            ; Event declined

                           / "TENTATIVE"           ; Event tentatively
                                                   ; accepted
                           / "DELEGATED"           ; Event delegated
                           / x-name                ; Experimental status
                           / iana-token)        ; Other IANA registered
                                                   ; status
        ; These <As defined by any IETF RFC>

   Description: This data type might be used to reference binary
      information, for values that are large, or otherwise undesirable
      to include directly in the participation statuses for a "VEVENT".
        ; Default is NEEDS-ACTION
        partstatparam      /= "PARTSTAT" "="
                            ("NEEDS-ACTION"        ; To-do needs action
                           / "ACCEPTED"            ; To-do accepted
                           / "DECLINED"            ; To-do declined
                           / "TENTATIVE"           ; To-do tentatively
                                          ; accepted
                           / "DELEGATED"           ; To-do delegated
                           / "COMPLETED"           ; To-do completed.
                                          ; COMPLETED property has
                                          ;date/time completed.
                           / "IN-PROCESS"          ; To-do iCalendar object.

      The URI value formats in process of
                                          ; being completed
                           / x-name              ; Experimental status
                          / iana-token)         ; Other RFC 1738, RFC 2111 and any other IETF
      registered value format can be specified.

      Any IANA registered
                                          ; status
        ; URI format can be used.  These include, but
      are the participation statuses for not limited to, those defined in RFC 1738 and RFC 2111.

      When a "VTODO". Default property parameter value is
        ; NEEDS-ACTION

        partstatparam      /= "PARTSTAT" "="
                        ("NEEDS-ACTION"        ; Journal needs action
                       / "ACCEPTED"            ; Journal accepted
                       / "DECLINED"            ; Journal declined
                      / x-name             ; Experimental status
                     / iana-token)        ; Other IANA registered
                                             ; status
        ; These are a URI value type, the participation statuses for URI MUST
      be specified as a "VJOURNAL".
        ; Default quoted-string value.

      No additional content value encoding (i.e., BACKSLASH character
      encoding) is NEEDS-ACTION defined for this value type.

   Example:

        ATTENDEE;PARTSTAT=DECLINED:MAILTO:jsmith@host.com

8.2.13.  Status

   Property Name: STATUS

   Purpose: This property defines the overall status or confirmation The following is a URI for
   the calendar component. a network file:

        http://host1.com/my-report.txt

3.3.14.  UTC Offset
   Value Type: TEXT

   Property Parameters: Non-standard property parameters can be
   specified on this property.

   Conformance: Name: UTC-OFFSET

   Purpose: This property can be specified in "VEVENT", "VTODO" or
   "VJOURNAL" calendar components.

   Description: In a group scheduled calendar component, the property value type is used by the "Organizer" to provide a confirmation of the event identify properties that contain
      an offset from UTC to the
   "Attendees".  For example in a "VEVENT" calendar component, the
   "Organizer" can indicate that a meeting is tentative, confirmed or
   cancelled.  In a "VTODO" calendar component, the "Organizer" can
   indicate that an action item needs action, is completed, is in
   process or being worked on, or has been cancelled.  In a "VJOURNAL"
   calendar component, the "Organizer" can indicate that a journal entry
   is draft, final or has been cancelled or removed. local time.

   Format Definition: The property data type is defined by the following
      notation:

        status     = "STATUS" statparam] ":" statvalue CRLF

        statparam

        utc-offset = *(";" xparam)

        statvalue time-numzone  ;As defined above in time data type

        time-numzone       = "TENTATIVE"           ;Indicates event is
                                           ;tentative.
                   / "CONFIRMED"           ;Indicates event is
                                           ;definite. ("+" / "CANCELLED"           ;Indicates event was
                                           ;cancelled.
           ;Status values "-") time-hour time-minute [time-
        second]

   Description: The PLUS SIGN character MUST be specified for a "VEVENT"

        statvalue  =/ "NEEDS-ACTION"      ;Indicates to-do needs action.
                   / "COMPLETED"      ;Indicates to-do completed.
                   / "IN-PROCESS"      ;Indicates to-do in process positive
      UTC offsets (i.e., ahead of
                   / "CANCELLED"      ;Indicates to-do was cancelled.
           ;Status values UTC).  The MINUS SIGN character MUST
      be specified for "VTODO".

        statvalue  =/ "DRAFT"      ;Indicates journal is draft.
                   / "FINAL"               ;Indicates journal is final.
                   / "CANCELLED"    ;Indicates journal negative UTC offsets (i.e., behind of UTC).  The
      value of "-0000" and "-000000" are not allowed.  The time-second,
      if present, may not be 60; if absent, it defaults to zero.

      No additional content value encoding (i.e., BACKSLASH character
      encoding) is removed.
           ;Status values defined for "VJOURNAL". this value type.

   Example: The following UTC offsets are given for standard time for
      New York (five hours behind UTC) and Geneva (one hour ahead of
      UTC):

        -0500

        +0100

3.4.  iCalendar Object

   The Calendaring and Scheduling Core Object is an example a collection of
   calendaring and scheduling information.  Typically, this property for information
   will consist of a "VEVENT"
   calendar component:

        STATUS:TENTATIVE single iCalendar object.  However, multiple
   iCalendar objects can be sequentially grouped together.  The first
   line and last line of the iCalendar object MUST contain a pair of
   iCalendar object delimiter strings.  The syntax for an iCalendar
   object is as follows:

     icalobject = 1*("BEGIN" ":" "VCALENDAR" CRLF
                  icalbody
                  "END" ":" "VCALENDAR" CRLF)

   The following is an a simple example of this an iCalendar object:

     BEGIN:VCALENDAR
     VERSION:2.0
     PRODID:-//hacksw/handcal//NONSGML v1.0//EN
     BEGIN:VEVENT
     DTSTART:19970714T170000Z
     DTEND:19970715T035959Z
     SUMMARY:Bastille Day Party
     END:VEVENT
     END:VCALENDAR

3.5.  Property

   A property for is the definition of an individual attribute describing a "VTODO"
   calendar
   component:

        STATUS:NEEDS-ACTION or a calendar component.  A property takes the form defined
   by the "contentline" notation defined in Section 3.1.

   The following is an example of this property for a "VJOURNAL"
   calendar component:

        STATUS:DRAFT

8.2.14.  Summary

   Property Name: SUMMARY

   Purpose: property:

     DTSTART:19960415T133000Z

   This property defines a short summary or subject for the
   calendar component.

   Value Type: TEXT memo imposes no ordering of properties within an iCalendar
   object.

   Property Parameters: Non-standard, alternate text representation names, parameter names and
   language property parameters can be specified on this property.

   Conformance: The property can be specified in "VEVENT", "VTODO",
   "VJOURNAL" or "VALARM" calendar components.

   Description: This enumerated parameter values are
   case insensitive.  For example, the property name "DUE" is used in the "VEVENT", "VTODO" same
   as "due" and
   "VJOURNAL" calendar components to capture a short, one line summary
   about the activity or journal entry.

   This property "Due", DTSTART;TZID=US-Eastern:19980714T120000 is used in the "VALARM" calendar component to capture
   same as DtStart;TzID=US-Eastern:19980714T120000.

3.6.  Calendar Components

   The body of the subject iCalendar object consists of an EMAIL category a sequence of calendar
   properties and one or more calendar components.  The calendar
   properties are attributes that apply to the calendar as a whole.  The
   calendar components are collections of properties that express a
   particular calendar semantic.  For example, the calendar component
   can specify an event, a to-do, a journal entry, time zone
   information, or free/busy time information, or an alarm.

   Format Definition:

   The property body of the iCalendar object is defined by the following
   notation:

        summary

     icalbody   = "SUMMARY" summparam ":" text CRLF

        summparam calprops component

     calprops   = *( 2*(

                ; the following 'prodid' and 'version' are optional, both REQUIRED,
                ; but MUST NOT occur more than once

                   (";" altrepparam) / (";" languageparam)

                prodid /version /

                ; the following is 'calscale' and 'method' are optional,
                ; and MAY but MUST NOT occur more than once

                   (";" xparam)

                calscale        /
                method          /

                x-prop
                )

   Example: The following is an example of this property:

        SUMMARY:Department Party

8.2.15.  Date and Time Component Properties

   The following properties specify date and time related information in
   calendar components.

8.2.15.1.  Date/Time Completed

   Property Name: COMPLETED

   Purpose: This property defines the date and time that a to-do was
   actually completed.

   Value Type: DATE-TIME
   Property Parameters: Non-standard property parameters can be
   specified on this property.

   Conformance: The property can be specified in a "VTODO" calendar
   component.

   Description: The date and time MUST be in a UTC format.

   Format Definition: The property is defined by the following notation:

        completed

     component  = "COMPLETED" compparam 1*(eventc / todoc / journalc / freebusyc /
                / timezonec / iana-comp / x-comp)

     iana-comp  = "BEGIN" ":" date-time iana-token CRLF

        compparam

                  1*contentline

                  "END" ":" iana-token CRLF

     x-comp     = *(";" xparam)

   Example: The following is an example of this property:

        COMPLETED:19960401T235959Z

8.2.15.2.  Date/Time End

   Property Name: DTEND

   Purpose: This property specifies "BEGIN" ":" x-name CRLF

                  1*contentline

                  "END" ":" x-name CRLF

   An iCalendar object MUST include the date "PRODID" and time that a "VERSION" calendar
   component ends.

   Value Type: The default value type is DATE-TIME.  The value type can
   be set
   properties.  In addition, it MUST include at least one calendar
   component.  Special forms of iCalendar objects are possible to
   publish just busy time (i.e., only a DATE value type.

   Property Parameters: Non-standard, value data type, "VFREEBUSY" calendar component)
   or time zone
   identifier property parameters can be specified on this property.

   Conformance: This property can be specified in "VEVENT" or
   "VFREEBUSY" (i.e., only a "VTIMEZONE" calendar components.

   Description: Within component)
   information.  In addition, a complex iCalendar object is possible
   that is used to capture a complete snapshot of the "VEVENT" contents of a
   calendar component, this property
   defines the date and time by which the event ends.  The value MUST be
   later in time than the value (e.g., composite of the "DTSTART" property.

   Within the "VFREEBUSY" many different calendar component, this property defines the
   end date and time for the free components).
   More commonly, an iCalendar object will consist of just a single
   "VEVENT", "VTODO" or busy time information.  The time
   MUST be specified in the UTC time format.  The value MUST be later in
   time than the value "VJOURNAL" calendar component.

3.6.1.  Event Component
   Component Name: VEVENT

   Purpose: Provide a grouping of the "DTSTART" property. component properties that describe an
      event.

   Format Definition: The property A "VEVENT" calendar component is defined by the
      following notation:

        dtend

       eventc     = "DTEND" dtendparam":" dtendval "BEGIN" ":" "VEVENT" CRLF

        dtendparam
                    eventprop *alarmc
                    "END" ":" "VEVENT" CRLF

       eventprop  = *(

                  ; the following are optional,
                  ; but MUST NOT occur more than once

                   (";" "VALUE" "=" ("DATE-TIME"

                  class / "DATE")) created /
                   (";" tzidparam) description / dtstart / geo /
                  last-mod / location / organizer / priority /
                  dtstamp / seq / status / summary / transp /
                  uid / url / recurid /

                  ; either 'dtend' or 'duration' may appear in
                  ; a 'eventprop', but 'dtend' and 'duration'
                  ; MUST NOT occur in the same 'eventprop'

                  dtend / duration /

                  ; the following is are optional,
                  ; and MAY occur more than once

                   (";" xparam)

                   )

        dtendval   = date-time

                  attach / date
        ;Value MUST match value type

   Example: The following attendee / categories / comment /
                  contact / exdate / exrule / rstatus / related /
                  resources / rdate / rrule / x-prop

                  )

   Description: A "VEVENT" calendar component is an example a grouping of this property:

        DTEND:19960401T235959Z

        DTEND;VALUE=DATE:19980704

8.2.15.3.  Date/Time Due

   Property Name: DUE

   Purpose: This property defines the date component
      properties, and time possibly including "VALARM" calendar components,
      that represents a to-do is
   expected to be completed.

   Value Type: The default value type is DATE-TIME.  The value type scheduled amount of time on a calendar.  For
      example, it can be set to an activity; such as a DATE value type.

   Property Parameters: Non-standard, value data type, one-hour long,
      department meeting from 8:00 AM to 9:00 AM, tomorrow.  Generally,
      an event will take up time zone
   identifier property parameters can be specified on this property.

   Conformance: The property can be specified once an individual calendar.  Hence, the
      event will appear as an opaque interval in a "VTODO" calendar
   component.

   Description: The value MUST be a date/time equal search for busy time.
      Alternately, the event can have its Time Transparency set to or after
      "TRANSPARENT" in order to prevent blocking of the
   DTSTART value, if specified.

   Format Definition: event in
      searches for busy time.

      The property "VEVENT" is defined by the following notation:

        due        = "DUE" dueparam":" dueval CRLF

        dueparam   = *(
                   ; the following are optional,
                   ; but MUST NOT occur more than once

                   (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
                   (";" tzidparam) /

                   ; also the following is optional,
                   ; and MAY occur more than once

                     *(";" xparam)

                   )

        dueval     = date-time / date
        ;Value MUST match calendar component used to specify an
      anniversary or daily reminder within a calendar.  These events
      have a DATE value type

   Example: The following is an example of this property:

        DUE:19980430T235959Z

8.2.15.4.  Date/Time Start

   Property Name: DTSTART

   Purpose: This for the "DTSTART" property specifies when instead of the calendar component begins.

   Value Type: The
      default value data type is of DATE-TIME.  The time value  If such a "VEVENT" has a "DTEND"
      property, it MUST be one of the forms defined for the DATE-TIME specified as a DATE value type. also.  The value
      anniversary type of "VEVENT" can be span more than one date (i.e,
      "DTEND" property value is set to a DATE value type.

   Property Parameters: Non-standard, value data type, time zone
   identifier property parameters can be specified on this property.

   Conformance: This property can be specified in the "VEVENT", "VTODO",
   "VFREEBUSY", or "VTIMEZONE" calendar components.

   Description: Within date after the "VEVENT" calendar component, this
      "DTSTART" property
   defines value).

      The "DTSTART" property for a "VEVENT" specifies the inclusive
      start date and time for of the event.  For recurring events, it also specifies the
      very first instance in the recurrence set.  The "DTEND" property is
   REQUIRED in
      for a "VEVENT" calendar components.  Events can have a start
   date/time but no end date/time.  In that case, component specifies the event does not
   take up any time.

   Within non-inclusive end
      of the "VFREEBUSY" event.  For cases where a "VEVENT" calendar component, this component
      specifies a "DTSTART" property defines with a DATE data type but no
      "DTEND" property, the
   start date and time for events non-inclusive end is the free or busy time information.  The time
   MUST be end of the
      calendar date specified in UTC time.

   Within by the "VTIMEZONE" "DTSTART" property.  For cases
      where a "VEVENT" calendar component, this component specifies a "DTSTART" property defines
      with a DATE-TIME data type but no "DTEND" property, the
   effective start event ends
      on the same calendar date and time of day specified by the
      "DTSTART" property.

      The "VEVENT" calendar component cannot be nested within another
      calendar component.  However, "VEVENT" calendar components can be
      related to each other or to a "VTODO" or to a "VJOURNAL" calendar
      component with the "RELATED-TO" property.

   Example: The following is an example of the "VEVENT" calendar
      component used to represent a meeting that will also be opaque to
      searches for busy time:

       BEGIN:VEVENT
       UID:19970901T130000Z-123401@host.com
       DTSTAMP:19970901T130000Z
       DTSTART:19970903T163000Z
       DTEND:19970903T190000Z
       SUMMARY:Annual Employee Review
       CLASS:PRIVATE
       CATEGORIES:BUSINESS,HUMAN RESOURCES
       END:VEVENT

      The following is an example of the "VEVENT" calendar component
      used to represent a time zone specification.  This
   property reminder that will not be opaque, but rather
      transparent, to searches for busy time:

       BEGIN:VEVENT
       UID:19970901T130000Z-123402@host.com
       DTSTAMP:19970901T130000Z
       DTSTART:19970401T163000Z
       DTEND:19970402T010000Z
       SUMMARY:Laurel is REQUIRED within each STANDARD and DAYLIGHT part included in "VTIMEZONE" sensitivity awareness class.
       CLASS:PUBLIC
       CATEGORIES:BUSINESS,HUMAN RESOURCES
       TRANSP:TRANSPARENT
       END:VEVENT

      The following is an example of the "VEVENT" calendar components and MUST be specified component
      used to represent an anniversary that will occur annually.  Since
      it takes up no time, it will not appear as opaque in a local
   DATE-TIME without search for
      busy time; no matter what the "TZID" value of the "TRANSP" property parameter.
      indicates:

       BEGIN:VEVENT
       UID:19970901T130000Z-123403@host.com
       DTSTAMP:19970901T130000Z
       DTSTART:19971102
       SUMMARY:Our Blissful Anniversary
       CLASS:CONFIDENTIAL
       CATEGORIES:ANNIVERSARY,PERSONAL,SPECIAL OCCASION
       RRULE:FREQ=YEARLY
       END:VEVENT

3.6.2.  To-do Component

   Component Name: VTODO

   Purpose: Provide a grouping of calendar properties that describe a
      to-do.

   Format Definition: The property A "VTODO" calendar component is defined by the
      following notation:

        dtstart

       todoc      = "DTSTART" dtstparam "BEGIN" ":" dtstval "VTODO" CRLF

        dtstparam
                    todoprop *alarmc
                    "END" ":" "VTODO" CRLF

       todoprop   = *(

                  ; the following are optional,
                  ; but MUST NOT occur more than once

                   (";" "VALUE" "=" ("DATE-TIME"

                  class / "DATE")) completed /
                   (";" tzidparam) created / description / dtstamp /
                  dtstart / geo / last-mod / location / organizer /
                  percent / priority / recurid / seq / status /
                  summary / uid / url /

                  ; either 'due' or 'duration' may appear in
                  ; a 'todoprop', but 'due' and 'duration'
                  ; MUST NOT occur in the same 'todoprop'

                  due / duration /

                  ; the following is are optional,
                  ; and MAY occur more than once

                     *(";" xparam)

                   )

        dtstval    = date-time
                  attach / date
        ;Value MUST match value type

   Example: The following attendee / categories / comment / contact /
                  exdate / exrule / rstatus / related / resources /
                  rdate / rrule / x-prop

                  )

   Description: A "VTODO" calendar component is an example of this property:

        DTSTART:19980118T073000Z

8.2.15.5.  Duration

   Property Name: DURATION

   Purpose: The property specifies a positive duration grouping of time.

   Value Type: DURATION
   Property Parameters: Non-standard property parameters can be
   specified on this property.

   Conformance: The property component
      properties and possibly "VALARM" calendar components that
      represent an action-item or assignment.  For example, it can be specified
      used to represent an item of work assigned to an individual; such
      as "turn in "VEVENT", "VTODO",
   "VFREEBUSY" or "VALARM" calendar components.

   Description: In a "VEVENT" travel expense today".

      The "VTODO" calendar component the property may cannot be
   used to specify a duration of the event, instead of an explicit end
   date/time.  In a nested within another
      calendar component.  However, "VTODO" calendar component the property may components can be used
      related to each other or to specify a duration for the to-do, instead of an explicit due date/
   time.  In "VTODO" or to a "VFREEBUSY" "VJOURNAL" calendar
      component with the property may be used
   to specify the interval of free time being requested.  In a "VALARM" "RELATED-TO" property.

      A "VTODO" calendar component without the property may "DTSTART" and "DUE" (or
      "DURATION") properties specifies a to-do that will be used to specify the delay
   period prior to repeating an alarm.

   Format Definition: The property associated
      with each successive calendar date, until it is defined by the following notation:

        duration   = "DURATION" durparam ":" dur-value CRLF
                     ;consisting of a positive duration of time.

        durparam   = *(";" xparam) completed.

   Example: The following is an example of this property that specifies
   an interval of time of 1 hour and zero minutes and zero seconds:

        DURATION:PT1H0M0S

   The following is an example of this property that specifies an
   interval of time of 15 minutes.

        DURATION:PT15M

8.2.15.6.  Free/Busy Time

   Property Name: FREEBUSY

   Purpose: The property defines one or more free or busy time
   intervals.

   Value Type: PERIOD.  The date and time values MUST be in an UTC time
   format.

   Property Parameters: Non-standard or free/busy time type property
   parameters can be specified on this property.

   Conformance: The property can be specified in a "VFREEBUSY" "VTODO" calendar
   component.

   Property Parameter: "FBTYPE" and non-standard parameters can be
   specified on this property.

   Description: These time periods can be specified as either a start
   and end date-time or a start date-time and duration.  The date and
   time MUST be component:

       BEGIN:VTODO
       UID:19970901T130000Z-123404@host.com
       DTSTAMP:19970901T130000Z
       DTSTART:19970415T133000Z
       DUE:19970416T045959Z
       SUMMARY:1996 Income Tax Preparation
       CLASS:CONFIDENTIAL
       CATEGORIES:FAMILY,FINANCE
       PRIORITY:1
       STATUS:NEEDS-ACTION
       END:VTODO

3.6.3.  Journal Component

   Component Name: VJOURNAL

   Purpose: Provide a UTC time format.

   "FREEBUSY" properties within the "VFREEBUSY" calendar component
   SHOULD be sorted in ascending order, based on start time and then end
   time, with the earliest periods first.

   The "FREEBUSY" property can specify more than one value, separated by
   the COMMA character (US-ASCII decimal 44).  In such cases, the
   "FREEBUSY" property values SHOULD all be of the same "FBTYPE"
   property parameter type (e.g., all values grouping of component properties that describe a particular "FBTYPE"
   listed together in a single property).
      journal entry.

   Format Definition: The property A "VJOURNAL" calendar component is defined by the
      following notation:

        freebusy

       journalc   = "FREEBUSY" fbparam "BEGIN" ":" fbvalue "VJOURNAL" CRLF

        fbparam
                    jourprop
                    "END" ":" "VJOURNAL" CRLF

       jourprop   = *(

                  ; the following is are optional,
                  ; but MUST NOT occur more than once

                   (";" fbtypeparam)

                  class / created / description / dtstart / dtstamp /
                  last-mod / organizer / recurid / seq / status /
                  summary / uid / url /

                  ; the following is are optional,
                  ; and MAY occur more than once

                   (";" xparam)

                  attach / attendee / categories / comment /
                  contact / exdate / exrule / related / rdate /
                  rrule / rstatus / x-prop
                  )

        fbvalue    = period *["," period]
        ;Time value MUST be in the UTC time format.

   Example: The following are some examples of this property:

        FREEBUSY;FBTYPE=BUSY-UNAVAILABLE:19970308T160000Z/PT8H30M

        FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H

       FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H,
         19970308T230000Z/19970309T000000Z

8.2.15.7.  Time Transparency

   Property Name: TRANSP

   Purpose: This property defines whether an event

   Description: A "VJOURNAL" calendar component is transparent or not
   to busy time searches.

   Value Type: TEXT

   Property Parameters: Non-standard property parameters can be
   specified on this property.

   Conformance: This property can be specified once in a "VEVENT" grouping of
      component properties that represent one or more descriptive text
      notes associated with a particular calendar component.

   Description: Time Transparency date.  The "DTSTART"
      property is used to specify the characteristic of an event calendar date that
   determines whether the journal
      entry is associated with.  Generally, it appears will have a DATE value
      data type, but it can also be used to consume time on specify a calendar.  Events
   that consume actual time DATE-TIME value
      data type.  Examples of a journal entry include a daily record of
      a legislative body or a journal entry of individual telephone
      contacts for the individual day or resource associated

   with an ordered list of accomplishments for the
      day.  The "VJOURNAL" calendar SHOULD component can also be recorded as OPAQUE, allowing them used to be
   detected by free-busy time searches.  Other events, which do
      associate a document with a calendar date.

      The "VJOURNAL" calendar component does not take up the individual's (or resource's) time SHOULD be recorded as
   TRANSPARENT, making them invisible to free-busy time searches.

   Format Definition: The property is specified by the following
   notation:

        transp     = "TRANSP" tranparam ":" transvalue CRLF

        tranparam  = *(";" xparam)

        transvalue = "OPAQUE"   ;Blocks or opaque on a
      calendar.  Hence, it does not play a role in free or busy time searches.
                   / "TRANSPARENT" ;Transparent on busy
      searches - - it is as though it has a time searches.
           ;Default transparency value is OPAQUE

   Example: The following is an example of this property for an event
   that
      TRANSPARENT.  It is transparent to any such searches.

      The "VJOURNAL" calendar component cannot be nested within another
      calendar component.  However, "VJOURNAL" calendar components can
      be related to each other or does not block on free/busy time searches:

        TRANSP:TRANSPARENT to a "VEVENT" or to a "VTODO" calendar
      component, with the "RELATED-TO" property.

   Example: The following is an example of this property for an event that is
   opaque or blocks on free/busy time searches:

        TRANSP:OPAQUE

8.2.16.  Time Zone Component Properties

   The following properties specify time zone information in calendar
   components.

8.2.16.1.  Time Zone Identifier

   Property Name: TZID

   Purpose: This property specifies the text value that uniquely
   identifies the "VTIMEZONE" "VJOURNAL" calendar component.

   Value Type: TEXT

   Property Parameters: Non-standard property parameters can be
   specified on
      component:

       BEGIN:VJOURNAL
       UID:19970901T130000Z-123405@host.com
       DTSTAMP:19970901T130000Z
       DTSTART;VALUE=DATE:19970317
       SUMMARY:Staff meeting minutes
       DESCRIPTION:1. Staff meeting: Participants include Joe\, Lisa
         and Bob. Aurora project plans were reviewed. There is currently
         no budget reserves for this property.

   Conformance: This property MUST be specified in project. Lisa will escalate to
         management. Next meeting on Tuesday.\n
         2. Telephone Conference: ABC Corp. sales representative called
         to discuss new printer. Promised to get us a "VTIMEZONE"
   calendar component.

   Description: This is the label demo by which Friday.\n
         3. Henry Miller (Handsoff Insurance): Car was totaled by tree.
         Is looking into a time zone calendar loaner car. 654-2323 (tel).
       END:VJOURNAL

3.6.4.  Free/Busy Component

   Component Name: VFREEBUSY

   Purpose: Provide a grouping of component is referenced by any iCalendar properties whose data type
   is that describe
      either DATE-TIME or TIME and not intended a request for free/busy time, describe a response to specify a UTC
      request for free/busy time or describe a
   "floating" time.  The presence published set of the SOLIDUS character (US-ASCII
   decimal 47) as a prefix, indicates that this TZID represents an
   unique ID in a globally defined time zone registry (when such
   registry is defined).

   Note: This document does not define a naming convention for time zone
   identifiers.  Implementers may want to use the naming conventions
   defined in existing time zone specifications such as the public-
   domain Olson database [TZ].  The specification of globally unique
   time zone identifiers is not addressed by this document and is left
   for future study.

   Format Definition: This property is defined by busy
      time.

   Format Definition: A "VFREEBUSY" calendar component is defined by the
      following notation:

        tzid

       freebusyc  = "TZID" tzidpropparam "BEGIN" ":" [tzidprefix] text "VFREEBUSY" CRLF

        tzidpropparam      = *(";" xparam)

        ;tzidprefix        = "/"
        ; Defined previously. Just listed here for reader convenience.

   Example: The following are examples of non-globally unique time zone
   identifiers:

        TZID:US-Eastern

        TZID:California-Los_Angeles

   The following is an example of a fictitious globally unique time zone
   identifier:

        TZID:/US-New_York-New_York

8.2.16.2.  Time Zone Name

   Property Name: TZNAME

   Purpose: This property specifies the customary designation for a time
   zone description.

   Value Type: TEXT

   Property Parameters: Non-standard and language property parameters
   can be specified on this property.

   Conformance: This property can be specified in a "VTIMEZONE" calendar
   component.

   Description: This property may be specified in multiple languages; in
   order to provide for different language requirements.

   Format Definition: This property is defined by the following
   notation:

        tzname     = "TZNAME" tznparam
                    fbprop
                    "END" ":" text "VFREEBUSY" CRLF

        tznparam

       fbprop     = *(

                  ; the following is are optional,
                  ; but MUST NOT occur more than once

                   (";" languageparam)

                  contact / dtstart / dtend / duration / dtstamp /
                  organizer / uid / url /

                  ; the following is are optional,
                  ; and MAY occur more than once

                   (";" xparam)

                  attendee / comment / freebusy / rstatus / x-prop
                  )
   Example: The following are example of this property:

        TZNAME:EST

   Figure 97

   The following

   Description: A "VFREEBUSY" calendar component is an example a grouping of this property when two different
   languages
      component properties that represents either a request for, a reply
      to a request for the free or busy time zone name are specified:

        TZNAME;LANGUAGE=en:EST
        TZNAME;LANGUAGE=fr-CA:HNE

8.2.16.3.  Time Zone Offset From

   Property Name: TZOFFSETFROM

   Purpose: This property specifies the offset which is in use prior information or a published set
      of busy time information.

      When used to
   this request free/busy time zone observance.

   Value Type: UTC-OFFSET

   Property Parameters: Non-standard property parameters can be
   specified on this property.

   Conformance: This information, the "ATTENDEE"
      property MUST be specified in a "VTIMEZONE" specifies the calendar component.

   Description: This users whose free/busy time is
      being requested; the "ORGANIZER" property specifies the offset calendar
      user who is requesting the free/busy time; the "DTSTART" and
      "DTEND" properties specify the window of time for which the free/
      busy time is in use prior being requested; the "UID" and "DTSTAMP" properties
      are specified to this assist in proper sequencing of multiple free/busy
      time observance.  It is requests.

      When used to calculate the absolute time
   at which the transition reply to a given observance takes place.  This request for free/busy time, the "ATTENDEE"
      property MUST only be specified in a "VTIMEZONE" specifies the calendar component.
   A "VTIMEZONE" user responding to the free/busy
      time request; the "ORGANIZER" property specifies the calendar component MUST include this property.  The user
      that originally requested the free/busy time; the "FREEBUSY"
      property value is a signed numeric indicating specifies the number of hours and
   possibly minutes from UTC.  Positive numbers represent free/busy time zones
   east of information (if it exists);
      and the prime meridian, or ahead "UID" and "DTSTAMP" properties are specified to assist in
      proper sequencing of UTC.  Negative numbers
   represent multiple free/busy time zones west of the prime meridian, or behind UTC.

   Format Definition: The property is defined by replies.

      When used to publish busy time, the following notation:

        tzoffsetfrom       = "TZOFFSETFROM" frmparam ":" utc-offset
                             CRLF

        frmparam   = *(";" xparam)
   Example: The following are examples of this property:

        TZOFFSETFROM:-0500

        TZOFFSETFROM:+1345

   Figure 100

8.2.16.4.  Time Zone Offset To

   Property Name: TZOFFSETTO

   Purpose: This "ORGANIZER" property specifies
      the offset which is in use in this
   time zone observance.

   Value Type: UTC-OFFSET

   Property Parameters: Non-standard property parameters can be
   specified on this property.

   Conformance: This property MUST be specified in a "VTIMEZONE" calendar component.

   Description: This property specifies user associated with the offset which is in use in
   this published busy time; the
      "DTSTART" and "DTEND" properties specify an inclusive time zone observance.  It is used to calculate window
      that surrounds the absolute busy time
   for information; the new observance.  The "FREEBUSY" property value is a signed numeric
   indicating the number of hours and possibly minutes from UTC.
   Positive numbers represent time zones east of
      specifies the prime meridian, or
   ahead of UTC.  Negative numbers represent published busy time zones west of information; and the
   prime meridian, or behind UTC.

   Format Definition: The "DTSTAMP"
      property is defined by specifies the following notation:

        tzoffsetto = "TZOFFSETTO" toparam ":" utc-offset CRLF

        toparam    = *(";" xparam)

   Example: The following are examples of this property:

        TZOFFSETTO:-0400

        TZOFFSETTO:+1245

   Figure 102

8.2.16.5.  Time Zone URL

   Property Name: TZURL

   Purpose: date/time that iCalendar object was
      created.

      The TZURL provides a means for a VTIMEZONE "VFREEBUSY" calendar component to
   point to a network location that can cannot be used to retrieve an up-to-
   date version of itself.

   Value Type: URI

   Property Parameters: Non-standard property parameters nested within another
      calendar component.  Multiple "VFREEBUSY" calendar components can
      be specified on this within an iCalendar object.  This permits the
      grouping of Free/Busy information into logical collections, such
      as monthly groups of busy time information.

      The "VFREEBUSY" calendar component is intended for use in
      iCalendar object methods involving requests for free time,
      requests for busy time, requests for both free and busy, and the
      associated replies.

      Free/Busy information is represented with the "FREEBUSY" property.

   Conformance:
      This property provides a terse representation of time periods.
      One or more "FREEBUSY" properties can be specified in a "VTIMEZONE" the
      "VFREEBUSY" calendar component.

   Description: The TZURL provides a means for

      When present in a VTIMEZONE component to
   point "VFREEBUSY" calendar component, the "DTSTART"
      and "DTEND" properties SHOULD be specified prior to any "FREEBUSY"
      properties.  In a network location that free time request, these properties can be used
      in combination with the "DURATION" property to retrieve an up-to-
   date version of itself.  This provides represent a hook to handle changes
   government bodies impose upon time zone definitions.  Retrieval of
   this resource results in an iCalendar object containing request
      for a single
   VTIMEZONE component and duration of free time within a METHOD property set to PUBLISH.

   Format Definition: specified window of time.

      The property is defined by recurrence properties ("RRULE", "EXRULE", "RDATE", "EXDATE")
      are not permitted within a "VFREEBUSY" calendar component.  Any
      recurring events are resolved into their individual busy time
      periods using the following notation:

        tzurl      = "TZURL" tzurlparam ":" uri CRLF

        tzurlparam = *(";" xparam) "FREEBUSY" property.

   Example: The following is an example of this property:

        TZURL:http://timezones.r.us.net/tz/US-California-Los_Angeles.ics

8.2.17.  Relationship Component Properties

   The following properties specify relationship information in calendar
   components.

8.2.17.1.  Attendee

   Property Name: ATTENDEE

   Purpose: The property defines an "Attendee" within a "VFREEBUSY" calendar
   component.

   Value Type: CAL-ADDRESS

   Property Parameters: Non-standard, language, calendar user type,
   group or list membership, participation role, participation status,
   RSVP expectation, delegatee, delegator, sent by, common name
      component used to request free or
   directory entry reference property parameters can be specified on
   this property.

   Conformance: This property MUST be specified in an iCalendar object
   that specifies a group scheduled calendar entity.  This property MUST
   NOT be specified in an iCalendar object when publishing the calendar
   information (e.g., NOT in an iCalendar object that specifies the
   publication of a calendar user's busy time, event, to-do or journal).
   This property is not specified in an iCalendar object that specifies
   only a time zone definition or that defines calendar entities that
   are not group scheduled entities, but are entities only on a single
   user's calendar.

   Description: The property MUST only be specified within calendar
   components to specify participants, non-participants and the chair of
   a group scheduled calendar entity. information:

       BEGIN:VFREEBUSY
       ORGANIZER:MAILTO:jane_doe@host1.com
       ATTENDEE:MAILTO:john_public@host2.com
       DTSTART:19971015T050000Z
       DTEND:19971016T050000Z
       DTSTAMP:19970901T083000Z
       END:VFREEBUSY

      The property following is specified within an "EMAIL" category example of the "VALARM" a "VFREEBUSY" calendar component
      used to specify an
   email address that is to receive the email type of iCalendar alarm.

   The property parameter CN is for the common or displayable name
   associated with the calendar address; ROLE, for the intended role
   that the attendee will have in the calendar component; PARTSTAT, for
   the status of the attendee's participation; RSVP, for indicating
   whether the favor of a reply is requested; CUTYPE, to indicate the
   type of calendar user; MEMBER, to indicate the groups that the
   attendee belongs to; DELEGATED-TO, to indicate the calendar users
   that the original request was delegated to; and DELEGATED-FROM, to
   indicate whom the request was delegated from; SENT-BY, to indicate
   whom is acting on behalf of the ATTENDEE; and DIR, to indicate the
   URI that points to the directory with busy time information:

       BEGIN:VFREEBUSY
       ORGANIZER:MAILTO:jane_doe@host1.com
       ATTENDEE:MAILTO:john_public@host2.com
       DTSTAMP:19970901T100000Z
       FREEBUSY;VALUE=PERIOD:19971015T050000Z/PT8H30M,
        19971015T160000Z/PT5H30M,19971015T223000Z/PT6H30M
       URL:http://host2.com/pub/busy/jpublic-01.ifb
       COMMENT:This iCalendar file contains busy time information corresponding to for
         the
   attendee.  These property parameters can be specified on an
   "ATTENDEE"

   property in either a "VEVENT", "VTODO" or "VJOURNAL" calendar
   component.  They MUST not be specified in next three months.
       END:VFREEBUSY

      The following is an "ATTENDEE" property in example of a "VFREEBUSY" or "VALARM" calendar component.  If the LANGUAGE property
   parameter is specified, the identified language applies component
      used to the CN
   parameter.

   A recipient delegated publish busy time information.

       BEGIN:VFREEBUSY
       ORGANIZER:jsmith@host.com
       DTSTART:19980313T141711Z
       DTEND:19980410T141711Z
       FREEBUSY:19980314T233000Z/19980315T003000Z
       FREEBUSY:19980316T153000Z/19980316T163000Z
       FREEBUSY:19980318T030000Z/19980318T040000Z
       URL:http://www.host.com/calendar/busytime/jsmith.ifb
       END:VFREEBUSY

3.6.5.  Time Zone Component

   Component Name: VTIMEZONE

   Purpose: Provide a request MUST inherit the RSVP and ROLE values
   from the attendee that delegated the request to them.

   Multiple attendees can be specified by including multiple "ATTENDEE" grouping of component properties within the calendar component. that defines a
      time zone.

   Format Definition: The property A "VTIMEZONE" calendar component is defined by the
      following notation:

        attendee

       timezonec  = "ATTENDEE" attparam "BEGIN" ":" cal-address "VTIMEZONE" CRLF

        attparam   = *(

                    2*(

                    ; the following 'tzid' is required, but MUST NOT occur more
                    ; than once

                  tzid /

                    ; 'last-mod' and 'tzurl' are optional,
                   ;
                  but MUST NOT occur more than once

                   (";" cutypeparam) / (";"memberparam) /
                   (";" roleparam) / (";" partstatparam) /
                   (";" rsvpparam) / (";" deltoparam)

                  last-mod /
                   (";" delfromparam) tzurl / (";" sentbyparam) /
                   (";"cnparam) / (";" dirparam)
                    ; one of 'standardc' or 'daylightc' MUST occur
                    ; and each MAY occur more than once.

                  standardc /
                   (";" languageparam) daylightc /

                  ; the following is optional,
                  ; and MAY occur more than once

                   (";" xparam)

                    x-prop

                    )

   Example: The following are examples of this property's use for a to-
   do:

        ORGANIZER:MAILTO:jsmith@host1.com
        ATTENDEE;MEMBER="MAILTO:DEV-GROUP@host2.com":
         MAILTO:joecool@host2.com
        ATTENDEE;DELEGATED-FROM="MAILTO:immud@host3.com":
         MAILTO:janedoe@host1.com

   The following is an example of this property used for specifying
   multiple attendees to an event:

        ORGANIZER:MAILTO:jsmith@host1.com
        ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;CN=Henry Cabot
         :MAILTO:hcabot@host2.com
        ATTENDEE;ROLE=REQ-PARTICIPANT;DELEGATED-FROM=
        "MAILTO:bob@host.com"
         ;PARTSTAT=ACCEPTED;CN=Jane Doe:MAILTO:jdoe@host1.com

   The following is an example of this property with a URI to the
   directory information associated with the attendee:

        ATTENDEE;CN=John Smith;DIR="ldap://host.com:6666/o=eDABC%
         20Industries,c=3DUS??(cn=3DBJim%20Dolittle)":MAILTO:jimdo@
         host1.com
   The following is an example of this property with "delegatee" and
   "delegator" information for an event:

        ORGANIZER;CN=John Smith:MAILTO:jsmith@host.com
        ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;DELEGATED-FROM=
         "MAILTO:iamboss@host2.com";CN=Henry Cabot:MAILTO:hcabot@
         host2.com
        ATTENDEE;ROLE=NON-PARTICIPANT;PARTSTAT=DELEGATED;DELEGATED-TO=
         "MAILTO:hcabot@host2.com";CN=The Big Cheese:MAILTO:iamboss
         @host2.com
        ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=ACCEPTED;CN=Jane Doe
         :MAILTO:jdoe@host1.com

   Example: The following is an example of this property's use when
   another calendar user is acting on behalf of the "Attendee":

        ATTENDEE;SENT-BY=MAILTO:jan_doe@host1.com;CN=John Smith:MAILTO:
         jsmith@host1.com

8.2.17.2.  Contact

   Property Name: CONTACT

   Purpose: The property is used to represent contact information or
   alternately a reference to contact information associated with the
   calendar component.

   Value Type: TEXT

   Property Parameters: Non-standard, alternate text representation and
   language property parameters can be specified on this property.

   Conformance: The property can be specified in a "VEVENT", "VTODO",
   "VJOURNAL" or "VFREEBUSY" calendar component.

   Description: The property value consists of textual contact
   information.  An alternative representation for the property value
   can also be specified that refers to a URI pointing to an alternate
   form, such as a vCard [RFC 2426], for the contact information.

   Format Definition: The property is defined by the following notation:

        contact

                    "END" ":" "VTIMEZONE" CRLF

       standardc  = "CONTACT" contparam "BEGIN" ":" text "STANDARD" CRLF

        contparam

                    tzprop

                    "END" ":" "STANDARD" CRLF

       daylightc  = *( "BEGIN" ":" "DAYLIGHT" CRLF

                    tzprop

                    "END" ":" "DAYLIGHT" CRLF

       tzprop     = 3*(

                  ; the following are optional, each REQUIRED,
                  ; but MUST NOT occur more than once

                   (";" altrepparam)

                  dtstart / (";" languageparam) tzoffsetto / tzoffsetfrom /

                  ; the following is are optional,
                  ; and MAY occur more than once

                   (";" xparam)

                  comment / rdate / rrule / tzname / x-prop

                  )

   Example: The following is an example of this property referencing
   textual contact information:

        CONTACT:Jim Dolittle\, ABC Industries\, +1-919-555-1234

   The following

   Description: A time zone is an example of this property with an alternate
   representation unambiguously defined by the set of time
      measurement rules determined by the governing body for a LDAP URI to given
      geographic area.  These rules describe at a directory entry containing minimum the
   contact information:

        CONTACT;ALTREP="ldap://host.com:6666/o=3DABC%20Industries\,
         c=3DUS??(cn=3DBJim%20Dolittle)":Jim Dolittle\, ABC Industries\,
         +1-919-555-1234

   The following is an example of this property with an alternate
   representation of a MIME body part containing base
      offset from UTC for the contact
   information, such time zone, often referred to as a vCard [RFC 2426] embedded the
      Standard Time offset.  Many locations adjust their Standard Time
      forward or backward by one hour, in a [MIME-DIR]
   content-type:

        CONTACT;ALTREP="CID:part3.msg970930T083000SILVER@host.com":Jim
          Dolittle\, ABC Industries\, +1-919-555-1234

   The following is an example order to accommodate seasonal
      changes in number of this property referencing a network
   resource, such daylight hours, often referred to as Daylight
      Saving Time.  Some locations adjust their time by a vCard [RFC 2426] object containing the contact
   information:

        CONTACT;ALTREP="http://host.com/pdi/jdoe.vcf":Jim
          Dolittle\, ABC Industries\, +1-919-555-1234

8.2.17.3.  Organizer

   Property Name: ORGANIZER

   Purpose: fraction of an
      hour.  Standard Time is also known as Winter Time.  Daylight
      Saving Time is also known as Advanced Time, Summer Time, or Legal
      Time in certain countries.  The property defines the organizer following table shows the changes
      in time zone rules in effect for New York City starting from 1967.
      Each line represents a calendar component.

   Value Type: CAL-ADDRESS

   Property Parameters: Non-standard, language, common name, directory
   entry reference, sent by property parameters can be specified on this
   property.

   Conformance: This property MUST be specified in an iCalendar object
   that specifies description or rule for a group scheduled calendar entity.  This property MUST
   be specified particular
      observance.

                         Effective Observance Rule

      +-----------+-------------------------+--------+--------------+
      | Date      | (Date/Time)             | Offset | Abbreviation |
      +-----------+-------------------------+--------+--------------+
      | 1967-*    | last Sun in an iCalendar object that specifies the publication of
   a calendar user's busy time.  This property MUST NOT be specified Oct, 02:00  | -0500  | EST          |
      | 1967-1973 | last Sun in
   an iCalendar object that specifies only Apr, 02:00  | -0400  | EDT          |
      | 1974-1974 | Jan 6, 02:00            | -0400  | EDT          |
      | 1975-1975 | Feb 23, 02:00           | -0400  | EDT          |
      | 1976-1986 | last Sun in Apr, 02:00  | -0400  | EDT          |
      | 1987-*    | first Sun in Apr, 02:00 | -0400  | EDT          |
      +-----------+-------------------------+--------+--------------+

       Effective Observance Rule

       Date       (Date/Time)             Offset  Abbreviation

       1967-*     last Sun in Oct, 02:00  -0500   EST

       1967-1973  last Sun in Apr, 02:00  -0400   EDT

       1974-1974  Jan 6,  02:00           -0400   EDT

       1975-1975  Feb 23, 02:00           -0400   EDT

       1976-1986  last Sun in Apr, 02:00  -0400   EDT

       1987-*     first Sun in Apr, 02:00 -0400   EDT

         Note: The specification of a global time zone definition or
   that defines calendar entities that are registry is not group scheduled entities,
   but are entities only on a single user's calendar.

   Description: The property
         addressed by this document and is specified within the "VEVENT", "VTODO",
   "VJOURNAL calendar components to specify left for future study.
         However, implementers may find the organizer of Olson time zone database
         [TZDB] a group
   scheduled calendar entity.  The property useful reference.  It is specified within the
   "VFREEBUSY" calendar component to specify the calendar user
   requesting the free or busy time.  When publishing a "VFREEBUSY"
   calendar component, the property an informal, public-domain
         collection of time zone information, which is currently being
         maintained by volunteer Internet participants, and is used to specify the calendar that
   the published busy in
         several operating systems.  This database contains current and
         historical time came from.

   The property has the property parameters CN, for specifying the
   common or display name associated with the "Organizer", DIR, zone information for
   specifying a pointer to wide variety of
         locations around the directory information associated globe; it provides a time zone identifier
         for every unique time zone rule set in actual use since 1970,
         with historical data going back to the
   "Organizer", SENT-BY, introduction of standard
         time.

      Interoperability between two calendaring and scheduling
      applications, especially for specifying another calendar user that recurring events, to-dos or journal
      entries, is
   acting dependent on behalf of the "Organizer". ability to capture and convey date
      and time information in an unambiguous format.  The non-standard parameters may
   also be specified on this property.  If the LANGUAGE property
   parameter specification
      of current time zone information is specified, the identified language applies integral to this behavior.

      If present, the CN
   parameter value.

   Format Definition: The property is defined by "VTIMEZONE" calendar component defines the following notation:

        organizer  = "ORGANIZER" orgparam ":"
                     cal-address CRLF

        orgparam   = *(

                   ; the following are optional,

                   ; but MUST NOT occur more than once

                   (";" cnparam) / (";" dirparam) / (";" sentbyparam) /
                   (";" languageparam) /

                   ; the following is optional,
                   ; set of
      Standard Time and MAY occur more than once

                   (";" xparam)

                   )

   Example: The following is an example Daylight Saving Time observances (or rules) for
      a particular time zone for a given interval of this property:

        ORGANIZER;CN=John Smith:MAILTO:jsmith@host1.com time.  The following is
      "VTIMEZONE" calendar component cannot be nested within other
      calendar components.  Multiple "VTIMEZONE" calendar components can
      exist in an example of iCalendar object.  In this property with situation, each "VTIMEZONE"
      MUST represent a pointer to the
   directory information associated with the organizer:

        ORGANIZER;CN=JohnSmith;DIR="ldap://host.com:6666/o=3DDC%20Associ
         ates,c=3DUS??(cn=3DJohn%20Smith)":MAILTO:jsmith@host1.com

   The following unique time zone definition.  This is an example necessary
      for some classes of this property used by another events, such as airline flights, that start in
      one time zone and end in another.

      The "VTIMEZONE" calendar
   user who is acting component MUST be present if the
      iCalendar object contains an RRULE that generates dates on behalf both
      sides of a time zone shift (e.g., both in Standard Time and
      Daylight Saving Time) unless the organizer, with responses
   intended iCalendar object intends to
      convey a floating time ( see Section 3.3.12 for proper
      interpretation of floating time).  It can be sent back to present if the organizer,
      iCalendar object does not the other calendar
   user:

        ORGANIZER;SENT-BY="MAILTO:jane_doe@host.com":
         MAILTO:jsmith@host1.com

8.2.17.4.  Participation Role

   Parameter Name: ROLE

   Purpose: To specify the participation role contain such a RRULE.  In addition, if a
      RRULE is present, there MUST be valid time zone information for the
      all recurrence instances.

      The "VTIMEZONE" calendar user
   specified by component MUST include the property.

   Description: This parameter can be specified on properties with "TZID"
      property and at least one definition of a
   CAL-ADDRESS value type. standard or daylight
      component.  The parameter specifies the participation
   role for standard or daylight component MUST include the
      "DTSTART", "TZOFFSETFROM" and "TZOFFSETTO" properties.

      An individual "VTIMEZONE" calendar user component MUST be specified for
      each unique "TZID" parameter value specified by the property in the group
   schedule iCalendar
      object.

      Each "VTIMEZONE" calendar component.  If not specified on component consists of a property collection of
      one or more sub-components that
   allows this parameter, describe the default value is REQ-PARTICIPANT.

   Format Definition: rule for a particular
      observance (either a Standard Time or a Daylight Saving Time
      observance).  The property parameter is defined by the following
   notation:

        roleparam  = "ROLE" "="
                    ("CHAIR"               ; Indicates chair "STANDARD" sub-component consists of the
                                           ; calendar entity
                 / "REQ-PARTICIPANT"   ; Indicates a participant whose
                                           ; participation is required
                 / "OPT-PARTICIPANT"   ; Indicates
      collection of properties that describe Standard Time.  The
      "DAYLIGHT" sub-component consists of a participant whose
                                           ; participation is optional
                 / "NON-PARTICIPANT"  ; Indicates collection of properties
      that describe Daylight Saving Time.  In general this collection of
      properties consists of:

         the first onset date-time for the observance

         the last onset date-time for the observance, if a participant who last onset is
                                          ; copied
         known.

         the offset to be applied for information
                                          ; purposes only
                 / x-name         ; Experimental role
                 / iana-token)   ; Other IANA role
        ; Default is REQ-PARTICIPANT

   Example:

        ATTENDEE;ROLE=CHAIR:MAILTO:mrbig@host.com

   Figure 121

8.2.17.5.  Sent By

   Parameter Name: SENT-BY

   Purpose: To specify the calendar user observance

         a rule that is acting on behalf of describes the
   calendar user specified by day and time when the property.

   Description: This parameter can be specified on properties with observance
         takes effect

         an optional name for the observance

      For a
   CAL-ADDRESS value type.  The parameter specifies given time zone, there may be multiple unique definitions of
      the calendar user
   that observances over a period of time.  Each observance is acting on behalf
      described using either a "STANDARD" or "DAYLIGHT" sub-component.
      The collection of these sub-components is used to describe the calendar user specified
      time zone for a given period of time.  The offset to apply at any
      given time is found by locating the
   property.  The parameter value MUST be a MAILTO URI as defined observance that has the last
      onset date and time before the time in
   [RFC 1738]. question, and using the
      offset value from that observance.

      The individual calendar address parameter values MUST
   each be specified top-level properties in a quoted-string.

   Format Definition: "VTIMEZONE" calendar component are:

      The mandatory "TZID" property parameter is defined by the following
   notation:

        sentbyparam        = "SENT-BY" "=" DQUOTE cal-address DQUOTE
   Example:

        ORGANIZER;SENT-BY:"MAILTO:sray@host.com":MAILTO:jsmith@host.com

   Figure 123

8.2.17.6.  Delegators

   Parameter Name: DELEGATED-FROM

   Purpose: To specify the calendar users a text value that have delegated their
   participation to uniquely
      identifies the VTIMEZONE; and each MAY occur more than once.
      calendar user specified by component within the property.

   Description: This parameter can be specified on properties with a
   CAL-ADDRESS value type.  This parameter can be specified on a scope of an iCalendar object.

      The optional "LAST-MODIFIED" property that has is a UTC value type of calendar address.  This parameter
   specifies those calendar uses that have delegated their participation
   in a group scheduled event or to-do to the calendar user specified by
      specifies the property. date and time that this time zone definition was
      last updated.

      The optional "TZURL" property is a url value MUST be that points to a MAILTO URI as defined in [RFC
   1738].  The individual calendar address parameter values MUST each be
   specified in
      published VTIMEZONE definition.  TZURL SHOULD refer to a quoted-string.

   Format Definition: The property parameter resource
      that is defined accessible by the following
   notation:

        delfromparam       = "DELEGATED-FROM" "="
                            DQUOTE cal-address DQUOTE
                     *("," DQUOTE cal-address DQUOTE)

   Example:

        ATTENDEE;DELEGATED-FROM="MAILTO:jsmith@host.com":MAILTO:
         jdoe@host.com

   Figure 125

8.2.17.7.  Delegatees

   Parameter Name: DELEGATED-TO

   Purpose: To specify the calendar users anyone who might need to whom the calendar user
   specified by interpret the property has delegated participation.

   Description:
      object.  This parameter can SHOULD NOT normally be specified on properties with a
   CAL-ADDRESS value type.  This parameter specifies those calendar
   users whom have been delegated participation in a group scheduled
   event "file" URL or to-do by the calendar user specified by other URL
      that is not widely-accessible.

      The collection of properties that are used to define the property. STANDARD
      and DAYLIGHT sub-components include:

      The
   value MUST be a MAILTO URI as defined mandatory "DTSTART" property gives the effective onset date
      and local time for the time zone sub-component definition.
      "DTSTART" in [RFC 1738].  The individual
   calendar address parameter values this usage MUST each be specified in as a quoted-
   string.

   Format Definition: local DATE-TIME
      value.

      The mandatory "TZOFFSETFROM" property parameter is defined by gives the following
   notation:

        deltoparam = "DELEGATED-TO" "=" DQUOTE cal-address DQUOTE
                     *("," DQUOTE cal-address DQUOTE)

   Example:

        ATTENDEE;DELEGATED-TO="MAILTO:jdoe@host.com","MAILTO:jqpublic@
         host.com":MAILTO:jsmith@host.com

8.2.17.8.  Common Name

   Parameter Name: CN

   Purpose: To specify UTC offset which
      is in use when the common name to be associated onset of this time zone observance begins.
      "TZOFFSETFROM" is combined with "DTSTART" to define the
   calendar user specified by the property.

   Description: This parameter can be specified on properties with a
   CAL-ADDRESS value type.  The parameter specifies effective
      onset for the common name to
   be associated with time zone sub-component definition.  For example,
      the calendar user specified by following represents the property. time at which the observance of
      Standard Time took effect in Fall 1967 for New York City:

       DTSTART:19671029T020000

       TZOFFSETFROM:-0400

      The
   parameter value mandatory "TZOFFSETTO " property gives the UTC offset for the
      time zone sub-component (Standard Time or Daylight Saving Time)
      when this observance is text. in use.

      The parameter value can be used optional "TZNAME" property is the customary name for display
   text the time
      zone.  It may be specified multiple times, to allow for specifying
      multiple language variants of the time zone names.  This could be associated with
      used for displaying dates.

      If specified, the calendar address specified by onset for the
   property.

   Format Definition: The property parameter is observance defined by the following
   notation:

        cnparam    = "CN" "=" param-value

   Example:

        ORGANIZER;CN="John Smith":MAILTO:jsmith@host.com

8.2.18.  Calendar User Type

   Parameter Name: CUTYPE

   Purpose: To specify the type of calendar user specified time
      zone sub-component is defined by either the "RRULE" or "RDATE"
      property.

   Description: This parameter  If neither is specified, only one sub-component can be
      specified on properties with a
   CAL-ADDRESS value type.  The parameter identifies in the type of "VTIMEZONE" calendar user specified by the property.  If not specified on a
   property component and it is assumed
      that allows this parameter, the default single observance specified is INDIVIDUAL.

   Format Definition: always in effect.

      The "RRULE" property parameter is defines the recurrence rule for the onset of
      the observance defined by this time zone sub-component.  Some
      specific requirements for the following
   notation:

        cutypeparam        = "CUTYPE" "="
                        ("INDIVIDUAL"        ; An individual
                        / "GROUP"              ; A group usage of individuals
                        / "RESOURCE"        ; A physical resource
                        / "ROOM"                ; A room resource
                        / "UNKNOWN"         ; Otherwise not known
                        / x-name                ; Experimental type
                        / iana-token)          ; Other IANA registered
                                                   ; type
                            ; Default RRULE for this purpose
      include:

         If observance is INDIVIDUAL

   Example:

        ATTENDEE;CUTYPE=GROUP:MAILTO:ietf-calsch@imc.org

8.2.19.  Directory Entry Reference

   Parameter Name: DIR

   Purpose: To known to have an effective end date, the
         "UNTIL" recurrence rule parameter MUST be used to specify reference the
         last valid onset of this observance (i.e., the UNTIL date-time
         will be equal to a directory entry associated with the calendar user specified last instance generated by the property.

   Description: This parameter can recurrence
         pattern).  It MUST be specified on properties with a
   CAL-ADDRESS value type. in UTC time.

         The parameter specifies a reference "DTSTART" and the "TZOFFSETTO" properties MUST be used when
         generating the onset date-time values (instances) from the
         RRULE.

      Alternatively, the "RDATE" property can be used to define the
   directory entry associated with
      onset of the calendar user specified observance by giving the
   property.  The parameter value is a URI.  The individual URI
   parameter values onset date and
      times.  "RDATE" in this usage MUST each be specified in as a quoted-string.

   Format Definition: local DATE-
      TIME value in UTC time.

      The optional "COMMENT" property parameter is defined by the following
   notation:

        dirparam   = "DIR" "=" DQUOTE uri DQUOTE also allowed for descriptive
      explanatory text.

   Example:

        ORGANIZER;DIR="ldap://host.com:6666/o=eDABC%20Industries,
        c=3DUS??(cn=3DBJim%20Dolittle)":MAILTO:jimdo@host1.com

8.2.20.  Recurrence ID

   Property Name: RECURRENCE-ID

   Purpose: The following are examples of the "VTIMEZONE" calendar
      component:

      This property is used in conjunction with an example showing time zone information for the "UID" and
   "SEQUENCE" property to identify a specific instance of Eastern
      United States using "RDATE" property.  Note that this is only
      suitable for a recurring
   "VEVENT", "VTODO" event that starts on or "VJOURNAL" calendar component.  The property
   value is later than April
      6, 1997 at 03:00:00 EDT (i.e., the earliest effective value of the "DTSTART" property of the
   recurrence instance.

   Value Type: The default value type transition
      date and time) and ends no later than April 7, 1998 02:00:00 EST
      (i.e., latest valid date and time for EST in this scenario).  For
      example, this property is DATE-TIME.
   The time format can be any of the valid forms defined used for a DATE-TIME
   value type.  See DATE-TIME value type definition for specific
   interpretations of recurring event that occurs every
      Friday, 8:00AM-9:00 AM, starting June 1, 1997, ending December 31,
      1997.

       BEGIN:VTIMEZONE
       TZID:US-Eastern
       LAST-MODIFIED:19870101T000000Z
       BEGIN:STANDARD
       DTSTART:19971026T020000
       RDATE:19971026T020000
       TZOFFSETFROM:-0400
       TZOFFSETTO:-0500
       TZNAME:EST
       END:STANDARD
       BEGIN:DAYLIGHT
       DTSTART:19970406T020000
       RDATE:19970406T020000
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       END:VTIMEZONE

      This is a simple example showing the various forms.  The value type can be set to
   DATE.

   Property Parameters: Non-standard property, value data type, current time zone identifier and recurrence identifier range parameters can be
   specified on this property.

   Conformance: This property can be specified in an iCalendar object
   containing a recurring calendar component.

   Description: The full range of calendar components specified by rules for
      the Eastern United States using a RRULE recurrence set pattern.  Note
      that there is referenced by referring to just the "UID" property
   value corresponding to the calendar component.  The "RECURRENCE-ID"
   property allows the reference no effective end date to an individual instance within the
   recurrence set.

   If the value either of the "DTSTART" property is a DATE type value, then the
   value MUST Standard Time
      or Daylight Time rules.  This information would be the calendar date valid for the recurrence instance.

   The date/time value a
      recurring event starting today and continuing indefinitely.

       BEGIN:VTIMEZONE
       TZID:US-Eastern
       LAST-MODIFIED:19870101T000000Z
       TZURL:http://zones.example.com/tz/US-Eastern.ics
       BEGIN:STANDARD
       DTSTART:19671029T020000
       RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
       TZOFFSETFROM:-0400
       TZOFFSETTO:-0500
       TZNAME:EST
       END:STANDARD
       BEGIN:DAYLIGHT
       DTSTART:19870405T020000
       RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       END:VTIMEZONE

      This is an example showing a fictitious set to of rules for the time when
      Eastern United States, where the original recurrence
   instance would occur; meaning Daylight Time rule has an
      effective end date (i.e., after that if the intent date, Daylight Time is to change a
   Friday meeting to Thursday, the date/time no
      longer observed).

       BEGIN:VTIMEZONE
       TZID:US--Fictitious-Eastern
       LAST-MODIFIED:19870101T000000Z
       BEGIN:STANDARD
       DTSTART:19671029T020000
       RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
       TZOFFSETFROM:-0400
       TZOFFSETTO:-0500
       TZNAME:EST
       END:STANDARD
       BEGIN:DAYLIGHT
       DTSTART:19870405T020000
       RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4;UNTIL=19980404T070000Z
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       END:VTIMEZONE
      This is still an example showing a fictitious set to of rules for the
   original Friday meeting.

   The "RECURRENCE-ID" property is used in conjunction with
      Eastern United States, where the "UID"
   and "SEQUENCE" property to identify a particular instance of a
   recurring event, to-do or journal.  For first Daylight Time rule has an
      effective end date.  There is a given pair of "UID" and
   "SEQUENCE" property values, second Daylight Time rule that
      picks up where the "RECURRENCE-ID" value for other left off.

       BEGIN:VTIMEZONE
       TZID:US--Fictitious-Eastern
       LAST-MODIFIED:19870101T000000Z
       BEGIN:STANDARD
       DTSTART:19671029T020000
       RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
       TZOFFSETFROM:-0400
       TZOFFSETTO:-0500
       TZNAME:EST
       END:STANDARD
       BEGIN:DAYLIGHT
       DTSTART:19870405T020000
       RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4;UNTIL=19980404T070000Z
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       BEGIN:DAYLIGHT
       DTSTART:19990424T020000
       RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=4
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       TZNAME:EDT
       END:DAYLIGHT
       END:VTIMEZONE

3.6.6.  Alarm Component

   Component Name: VALARM

   Purpose: Provide a
   recurrence instance is fixed.  When the definition grouping of the recurrence
   set for a component properties that define an
      alarm.

   Format Definition: A "VALARM" calendar component changes, and hence the "SEQUENCE"
   property value changes, is defined by the "RECURRENCE-ID" for a given recurrence
   instance might also change.The "RANGE" parameter is used to specify
   the effective range of recurrence instances from the instance
   specified by
      following notation:

       alarmc     = "BEGIN" ":" "VALARM" CRLF
                     (audioprop / dispprop / emailprop / procprop)
                     "END" ":" "VALARM" CRLF

       audioprop  = 2*(

                  ; 'action' and 'trigger' are both REQUIRED,
                  ; but MUST NOT occur more than once

                  action / trigger /

                  ; 'duration' and 'repeat' are both optional,
                  ; and MUST NOT occur more than once each,
                  ; but if one occurs, so MUST the "RECURRENCE-ID" property value.  The default value
   for other

                  duration / repeat /

                  ; the range parameter following is optional,
                  ; but MUST NOT occur more than once

                  attach /

                  ; the single recurrence instance only.  The
   value can also be "THISANDPRIOR" to indicate a range defined by the
   given recurrence instance following is optional,
                  ; and all prior instances or the value can be
   "THISANDFUTURE" to indicate a range defined by MAY occur more than once

                  x-prop

                  )

       dispprop   = 3*(

                  ; the given recurrence
   instance and following are all subsequent instances.

   Format Definition: The property is defined by REQUIRED,
                  ; but MUST NOT occur more than once

                  action / description / trigger /

                  ; 'duration' and 'repeat' are both optional,
                  ; and MUST NOT occur more than once each,
                  ; but if one occurs, so MUST the other

                  duration / repeat /

                  ; the following notation:

        recurid    = "RECURRENCE-ID" ridparam ":" ridval CRLF

        ridparam is optional,
                  ; and MAY occur more than once

                  x-prop

                  )

       emailprop  = *( 5*(

                  ; the following are optional, all REQUIRED,
                  ; but MUST NOT occur more than once

                   (";" "VALUE" "=" ("DATE-TIME"

                  action / "DATE)) description /
                   (";" tzidparam) trigger / (";" rangeparam) summary /
                  ; the following is REQUIRED,
                  ; and MAY occur more than once

                  attendee /

                  ; 'duration' and 'repeat' are both optional,
                  ; and MUST NOT occur more than once each,
                  ; but if one occurs, so MUST the other

                  duration / repeat /

                  ; the following are optional,
                  ; and MAY occur more than once

                   (";" xparam)

                  attach / x-prop

                  )

        ridval

       procprop   = date-time 3*(

                  ; the following are all REQUIRED,
                  ; but MUST NOT occur more than once

                  action / date
        ;Value attach / trigger /

                  ; 'duration' and 'repeat' are both optional,
                  ; and MUST match value type

   Example: The NOT occur more than once each,
                  ; but if one occurs, so MUST the other

                  duration / repeat /

                  ; 'description' is optional,
                  ; and MUST NOT occur more than once

                  description /

                  ; the following are examples is optional,
                  ; and MAY occur more than once

                  x-prop

                  )

   Description: A "VALARM" calendar component is a grouping of this property:

        RECURRENCE-ID;VALUE=DATE:19960401

        RECURRENCE-ID;RANGE=THISANDFUTURE:19960120T120000Z

   Figure 135

8.2.21.  Related To

   Property Name: RELATED-TO

   Purpose: The property component
      properties that is a reminder or alarm for an event or a to-do.
      For example, it may be used to represent define a relationship reminder for a pending
      event or
   reference between one an overdue to-do.

      The "VALARM" calendar component MUST include the "ACTION" and another.

   Value Type: TEXT

   Property Parameters: Non-standard and relationship type property
   parameters can be specified on this property.

   Conformance:
      "TRIGGER" properties.  The "ACTION" property can be specified one or more times in further constrains
      the
   "VEVENT", "VTODO" or "VJOURNAL" "VALARM" calendar components.

   Description: The property value consists of component in the persistent, globally
   unique identifier of another calendar component.  This value would be
   represented in a calendar component by following ways:

      When the "UID" property.

   By default, action is "AUDIO", the property value points alarm can also include one and
      only one "ATTACH" property, which MUST point to another calendar component
   that has a PARENT relationship sound resource,
      which is rendered when the alarm is triggered.

      When the action is "DISPLAY", the alarm MUST also include a
      "DESCRIPTION" property, which contains the text to be displayed
      when the referencing object.  The
   "RELTYPE" property parameter alarm is triggered.

      When the action is "EMAIL", the alarm MUST include a "DESCRIPTION"
      property, which contains the text to be used as the message body,
      a "SUMMARY" property, which contains the text to either explicitly state be used as the
   default PARENT relationship type
      message subject, and one or more "ATTENDEE" properties, which
      contain the email address of attendees to receive the referenced calendar component message.  It
      can also include one or more "ATTACH" properties, which are
      intended to override be sent as message attachments.  When the default PARENT relationship type alarm is
      triggered, the email message is sent.

      When the action is "PROCEDURE", the alarm MUST include one and specify
   either
      only one "ATTACH" property, which MUST point to a CHILD or SIBLING relationship.  The PARENT relationship
   indicates that procedure
      resource, which is invoked when the alarm is triggered.

      The "VALARM" calendar component is MUST only appear within either a subordinate of the
   referenced
      "VEVENT" or "VTODO" calendar component.  The CHILD relationship indicates that
   the  "VALARM" calendar component is
      components cannot be nested.  Multiple mutually independent
      "VALARM" calendar components can be specified for a superior of the referenced single
      "VEVENT" or "VTODO" calendar component.

      The SIBLING relationship indicates that "TRIGGER" property specifies when the calendar
   component is alarm will be triggered.
      The "TRIGGER" property specifies a peer of the referenced calendar component.

   Changes duration prior to the start of
      an event or a calendar component referenced by this to-do.  The "TRIGGER" edge may be explicitly set to
      be relative to the "START" or "END" of the event or to-do with the
      "RELATED" parameter of the "TRIGGER" property.  The "TRIGGER"
      property value type can have alternatively be set to an implicit impact absolute
      calendar date and time of day value.

      In an alarm set to trigger on the related calendar component.  For example,
   if a group "START" of an event changes its start or end date or time, then to-do,
      the
   related, dependent events will need to have their start and end dates
   changed "DTSTART" property MUST be present in a corresponding way.  Similarly, if a PARENT calendar
   component is canceled the associated event or deleted, then there is
      to-do.  In an implied impact to
   the related CHILD alarm in a "VEVENT" calendar components.  This property is intended
   only component set to provide information
      trigger on the relationship "END" of calendar
   components.  It is up to the target event, either the "DTEND" property
      MUST be present, or the "DTSTART" and "DURATION" properties MUST
      both be present.  In an alarm in a "VTODO" calendar system component set
      to maintain any
   property implications trigger on the "END" of this relationship.

   Format Definition: The property is defined by the following notation:

        related    = "RELATED-TO" [relparam] ":" text CRLF

        relparam   = *(

                   ; to-do, either the following is optional,
                   ; but "DUE" property
      MUST NOT occur more than once

                   (";" reltypeparam) /

                   ; be present, or the following is optional,
                   ; "DTSTART" and MAY occur more than once

                   (";" xparm)

                   ) "DURATION" properties MUST
      both be present.

      The following is an example alarm can be defined such that it triggers repeatedly.  A
      definition of this property:

        RELATED-TO:jsmith.part7.19960817T083000.xyzMail@host3.com

        RELATED-TO:19960401-080045-4000F192713-0052@host1.com

   Figure 137

8.2.22.  Uniform Resource Locator

   Property Name: URL

   Purpose: This property defines a Uniform Resource Locator (URL)
   associated an alarm with a repeating trigger MUST include both
      the iCalendar object.

   Value Type: URI

   Property Parameters: Non-standard property parameters can be
   specified on this property.

   Conformance: This "DURATION" and "REPEAT" properties.  The "DURATION" property can be specified once in
      specifies the "VEVENT",
   "VTODO", "VJOURNAL" or "VFREEBUSY" calendar components.

   Description: This delay period, after which the alarm will repeat.
      The "REPEAT" property may be used in a calendar component to
   convey a location where a more dynamic rendition of specifies the calendar
   information associated with number of additional
      repetitions that the calendar component can alarm will be found. triggered.  This memo does not attempt repetition
      count is in addition to standardize the form initial triggering of the URI, nor
   the format alarm.  Both
      of the resource pointed these properties MUST be present in order to by the property value. specify a
      repeating alarm.  If one of these two properties is absent, then
      the
   URL property and Content-Location MIME header are both specified,
   they MUST point to alarm will not repeat beyond the same resource.

   Format Definition: initial trigger.

      The "ACTION" property is defined by used within the following notation:

        url        = "URL" urlparam ":" uri CRLF

        urlparam   = *(";" xparam)

   Example: The following is an example of this property:

        URL:http://abc.com/pub/calendars/jsmith/mytime.ics

   Figure 139

8.2.23.  Unique Identifier

   Property Name: UID

   Purpose: This property defines "VALARM" calendar
      component to specify the persistent, globally unique
   identifier for type of action invoked when the calendar component.

   Value Type: TEXT

   Property Parameters: Non-standard property parameters can be
   specified on this property.

   Conformance: alarm is
      triggered.  The property MUST "VALARM" properties provide enough information for
      a specific action to be specified in invoked.  It is typically the "VEVENT", "VTODO",
   "VJOURNAL" or "VFREEBUSY" calendar components.

   Description: The UID itself MUST be a globally unique identifier.
   The generator
      responsibility of a "Calendar User Agent" (CUA) to deliver the identifier MUST guarantee that
      alarm in the identifier is
   unique.  There are several algorithms specified fashion.  An "ACTION" property value of
      AUDIO specifies an alarm that can causes a sound to be used played to accomplish
   this.  The identifier is RECOMMENDED alert
      the user; DISPLAY specifies an alarm that causes a text message to
      be the identical syntax displayed to the [RFC 822] addr-spec.  A good method user; EMAIL specifies an alarm that causes an
      electronic email message to assure uniqueness is be delivered to
   put the domain name one or more email
      addresses; and PROCEDURE specifies an alarm that causes a domain literal IP address
      procedure to be executed.  The "ACTION" property MUST specify one
      and only one of these values.

      In an AUDIO alarm, if the host on
   which the identifier was created on the right hand side of optional "ATTACH" property is included,
      it MUST specify an audio sound resource.  The intention is that
      the "@",
   and on sound will be played as the left hand side, put alarm effect.  If an "ATTACH"
      property is specified that does not refer to a combination of sound resource, or
      if the current calendar
   date and time of day (i.e., formatted in as a DATE-TIME value) along
   with some other currently unique (perhaps sequential) identifier
   available on the system (for example, a process id number).  Using a
   date/time value on the left hand side and a domain name specified sound resource cannot be rendered (because its
      format is unsupported, or domain
   literal on the right hand side makes because it possible to guarantee
   uniqueness since no two hosts should cannot be using retrieved), then
      the same domain name CUA or
   IP address at the same time.  Though other algorithms will work, it
   is RECOMMENDED that the right hand side contain some domain
   identifier (either of entity responsible for playing the host itself or otherwise) sound may
      choose a fallback action, such that the
   generator of the message identifier can guarantee the uniqueness of
   the left hand side within as playing a built-in default
      sound, or playing no sound at all.

      In a DISPLAY alarm, the scope of that domain.

   This intended alarm effect is the method for correlating scheduling messages with the
   referenced "VEVENT", "VTODO", or "VJOURNAL" calendar component.

   The full range text
      value of calendar components specified by a recurrence set
   is referenced by referring to just the "UID" "DESCRIPTION" property value
   corresponding to the calendar component.  The "RECURRENCE-ID"
   property allows the reference be displayed to the user.

      In an individual instance within EMAIL alarm, the
   recurrence set.

   This property intended alarm effect is an important method for group scheduling
   applications an email
      message to match requests with later replies, modifications or
   deletion requests.  Calendaring and scheduling applications MUST
   generate this property in "VEVENT", "VTODO" be composed and "VJOURNAL" calendar
   components delivered to assure interoperability with other group scheduling
   applications.  This identifier is created all the addresses
      specified by the "ATTENDEE" properties in the "VALARM" calendar system that
   generates an iCalendar object.

   Implementations MUST be able to receive and persist values of at
   least 255 characters for this property.

   Format Definition:
      component.  The "DESCRIPTION" property is defined by the following notation:

        uid        = "UID" uidparam ":" text CRLF

        uidparam   = *(";" xparam)

   Example: The following is an example of this property:

        UID:19960401T080045Z-4000F192713-0052@host1.com

   Figure 141

8.2.24.  Relationship Type

   Parameter Name: RELTYPE

   Purpose: To specify the type of hierarchical relationship associated
   with the "VALARM" calendar
      component specified by the property.

   Description: This parameter can MUST be specified on a property that
   references another related calendar.  The parameter specifies used as the
   hierarchical relationship type body text of the calendar component referenced
   by message, and the property.  The parameter value can
      "SUMMARY" property MUST be PARENT, to indicate that used as the referenced subject text.  Any "ATTACH"
      properties in the "VALARM" calendar component is a superior of calendar
   component; CHILD SHOULD be sent as
      attachments to indicate that the referenced calendar component
   is message.

      In a subordinate of PROCEDURE alarm, the calendar component; SIBLING to indicate that "ATTACH" property in the referenced "VALARM"
      calendar component is MUST specify a peer of procedure or program that is
      intended to be invoked as the calendar
   component. alarm effect.  If this parameter is not specified on an allowable
   property, the default relationship type procedure or
      program is PARENT.

   Format Definition: The in a format that cannot be rendered, then no procedure
      alarm will be invoked.  If the "DESCRIPTION" property parameter is defined by present,
      its value specifies the following
   notation:

        reltypeparam       = "RELTYPE" "="
                    ("PARENT"      ; Parent relationship. Default.
                     / "CHILD"       ; Child relationship
                     / "SIBLING      ; Sibling relationship
                     / iana-token    ; Some other IANA registered
                                           ; argument string to be passed to the
      procedure or program.  "Calendar User Agents" that receive an
      iCalendar relationship object with this category of alarm, can disable or allow
      the "Calendar User" to disable, or otherwise ignore this type
                     / x-name)       ; A non-standard, experimental
                                           ; relationship of
      alarm.  While a very useful alarm capability, the PROCEDURE type
      of alarm SHOULD be treated by the "Calendar User Agent" as a
      potential security risk.

   Example:

        RELATED-TO;RELTYPE=SIBLING:<19960401-080045-4000F192713
        @host.com>

   Figure 143

8.3.  Recurrence Component Properties The following properties specify recurrence information in example is for a "VALARM" calendar
   components.

8.3.1.  Exception Date/Times

   Property Name: EXDATE

   Purpose: This property defines component
      that specifies an audio alarm that will sound at a precise time
      and repeat 4 more times at 15 minute intervals:

       BEGIN:VALARM
       TRIGGER;VALUE=DATE-TIME:19970317T133000Z
       REPEAT:4
       DURATION:PT15M
       ACTION:AUDIO
       ATTACH;FMTTYPE=audio/basic:ftp://host.com/pub/sounds/bell-01.aud
       END:VALARM

      The following example is for a "VALARM" calendar component that
      specifies a display alarm that will trigger 30 minutes before the list
      scheduled start of the event or the due date/time exceptions of the to-do it
      is associated with and will repeat 2 more times at 15 minute
      intervals:

       BEGIN:VALARM
       TRIGGER:-PT30M
       REPEAT:2
       DURATION:PT15M
       ACTION:DISPLAY
       DESCRIPTION:Breakfast meeting with executive\n
        team at 8:30 AM EST.
       END:VALARM

      The following example is for a
   recurring "VALARM" calendar component.

   Value Type: component that
      specifies an email alarm that will trigger 2 days before the
      scheduled due date/time of a to-do it is associated with.  It does
      not repeat.  The default value type email has a subject, body and attachment link.

       BEGIN:VALARM
       TRIGGER:-P2D
       ACTION:EMAIL
       ATTENDEE:MAILTO:john_doe@host.com
       SUMMARY:*** REMINDER: SEND AGENDA FOR WEEKLY STAFF MEETING ***
       DESCRIPTION:A draft agenda needs to be sent out to the attendees
         to the weekly managers meeting (MGR-LIST). Attached is a
         pointer the document template for this property the agenda file.
       ATTACH;FMTTYPE=application/msword:http://host.com/templates/agen
        da.doc
       END:VALARM

      The following example is DATE-TIME. for a "VALARM" calendar component that
      specifies a procedural alarm that will trigger at a precise date/
      time and will repeat 23 more times at one hour intervals.  The value type can
      alarm will invoke a procedure file.

       BEGIN:VALARM
       TRIGGER;VALUE=DATE-TIME:19980101T050000Z
       REPEAT:23
       DURATION:PT1H
       ACTION:PROCEDURE
       ATTACH;FMTTYPE=application/octet-stream:ftp://host.com/novo-
        procs/felizano.exe
       END:VALARM

3.7.  Calendar Properties

   The Calendar Properties are attributes that apply to the iCalendar
   object, as a whole.  These properties do not appear within a calendar
   component.  They SHOULD be set specified after the "BEGIN:VCALENDAR"
   delimiter string and prior to DATE. any calendar component.

3.7.1.  Calendar Scale

   Property Name: CALSCALE

   Purpose: This property defines the calendar scale used for the
      calendar information specified in the iCalendar object.

   Value Type: TEXT

   Property Parameters: Non-standard, value data type and time zone
   identifier Non-standard property parameters can be
      specified on this property.

   Conformance: This property Property can be specified in an iCalendar object
   that includes a recurring calendar component.

   Description: The exception dates, if specified, are used in computing
   the recurrence set. object.  The recurrence set
      default value is "GREGORIAN".

   Description: This memo is based on the complete set of
   recurrence instances for a Gregorian calendar component. scale.  The recurrence set
      Gregorian calendar scale is
   generated by considering the initial "DTSTART" assumed if this property along with
   the "RRULE", "RDATE", "EXDATE" and "EXRULE" properties contained
   within is not
      specified in the iCalendar object.  It is expected that other
      calendar scales will be defined in other specifications or by
      future versions of this memo.

   Format Definition: The "DTSTART" property defines the
   first instance in is defined by the recurrence set.  Multiple instances following notation:

         calscale   = "CALSCALE" calparam ":" calvalue CRLF

         calparam   = *(";" xparam)

         calvalue   = "GREGORIAN" / iana-token

   Example: The following is an example of this property:

         CALSCALE:GREGORIAN

3.7.2.  Method

   Property Name: METHOD

   Purpose: This property defines the
   "RRULE" and "EXRULE" properties iCalendar object method associated
      with the calendar object.

   Value Type: TEXT

   Property Parameters: Non-standard property parameters can also be
      specified to define more
   sophisticated recurrence sets. on this property.

   Conformance: The final recurrence set is generated
   by gathering all of property can be specified in an iCalendar object.

   Description: When used in a MIME message entity, the start date-times generated by any value of this
      property MUST be the
   specified "RRULE" and "RDATE" properties, and then excluding any
   start date and times which fall within same as the union of start date and
   times generated by any specified "EXRULE" and "EXDATE" properties. Content-Type "method" parameter
      value.  This implies that start date and times property can only appear once within exclusion related
   properties (i.e., "EXDATE" and "EXRULE") take precedence over those
   specified by inclusion properties (i.e., "RDATE" and "RRULE").  Where
   duplicate instances are generated by the "RRULE" and "RDATE"
   properties, only one recurrence is considered.  Duplicate instances
   are ignored.

   The "EXDATE" iCalendar
      object.  If either the "METHOD" property can be used to exclude or the value specified in
   "DTSTART".  However, in such cases Content-Type
      "method" parameter is specified, then the original "DTSTART" date other MUST
   still also be maintained
      specified.

      No methods are defined by this specification.  This is the calendaring and scheduling system because
   the original "DTSTART" value has inherent usage dependencies by subject
      of other
   properties specifications, such as the "RECURRENCE-ID". iCalendar Transport-
      independent Interoperability Protocol (iTIP) defined by [I-D.ietf-
      calsify-2446bis].

      If this property is not present in the iCalendar object, then a
      scheduling transaction MUST NOT be assumed.  In such cases, the
      iCalendar object is merely being used to transport a snapshot of
      some calendar information; without the intention of conveying a
      scheduling semantic.

   Format Definition: The property is defined by the following notation:

        exdate

         method     = "EXDATE" exdtparam "METHOD" metparam ":" exdtval *("," exdtval) metvalue CRLF

        exdtparam

         metparam   = *(

                   ; the following are optional,
                   ; but MUST NOT occur more than once

                   (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /

                   (";" tzidparam) /

                   ; the following is optional,
                   ; and MAY occur more than once

                   (";" *(";" xparam)

                   )

        exdtval

         metvalue   = date-time / date
        ;Value MUST match value type iana-token

   Example: The following is an a hypothetical example of this property:

        EXDATE:19960402T010000Z,19960403T010000Z,19960404T010000Z

   Figure 145

8.3.2.  Exception Rule property to
      convey that the iCalendar object is a request for a meeting:

         METHOD:REQUEST

3.7.3.  Product Identifier

   Property Name: EXRULE PRODID

   Purpose: This property defines a rule or repeating pattern specifies the identifier for an
   exception to a recurrence set. the product that
      created the iCalendar object.

   Value Type: RECUR TEXT

   Property Parameters: Non-standard property parameters can be
      specified on this property.

   Conformance: This The property can MUST be specified once in "VEVENT", "VTODO" or
   "VJOURNAL" calendar components. an iCalendar
      object.

   Description: The exception rule, if specified, vendor of the implementation SHOULD assure that this
      is used a globally unique identifier; using some technique such as an
      FPI value, as defined in computing [ISO.9070.1991].

      This property SHOULD not be used to alter the recurrence set.  The recurrence set interpretation of an
      iCalendar object beyond the semantics specified in this memo.  For
      example, it is not to be used to further the complete set understanding of
   recurrence instances for a calendar component. non-
      standard properties.

   Format Definition: The recurrence set property is
   generated defined by considering the initial "DTSTART" property along with following notation:

         prodid     = "PRODID" pidparam ":" pidvalue CRLF

         pidparam   = *(";" xparam)

         pidvalue   = text
         ;Any text that describes the "RRULE", "RDATE", "EXDATE" product and "EXRULE" properties contained
   within the iCalendar object.  The "DTSTART" defines the first
   instance in the recurrence set.  Multiple instances version
         ;and that is generally assured of the "RRULE"
   and "EXRULE" properties can also be specified to define more
   sophisticated recurrence sets. being unique.

   Example: The final recurrence set following is generated
   by gathering all an example of this property.  It does not
      imply that English is the start date-times generated by any of default language.

         PRODID:-//ABC Corporation//NONSGML My Product//EN

3.7.4.  Version

   Property Name: VERSION

   Purpose: This property specifies the
   specified "RRULE" and "RDATE" properties, and excluding any start
   date and times which fall within identifier corresponding to the union of start date and times
   generated by any specified "EXRULE" and "EXDATE" properties.  This
   implies that start date and times within exclusion related properties
   (i.e., "EXDATE" and "EXRULE") take precedence over those specified by
   inclusion

   properties (i.e., "RDATE" and "RRULE").  Where duplicate instances
   are generated by
      highest version number or the "RRULE" minimum and "RDATE" properties, only one
   recurrence maximum range of the
      iCalendar specification that is considered.  Duplicate instances are ignored.

   The "EXRULE" required in order to interpret the
      iCalendar object.

   Value Type: TEXT

   Property Parameters: Non-standard property parameters can be used to exclude the value
      specified in
   "DTSTART".  However, in such cases the original "DTSTART" date on this property.

   Conformance: This property MUST
   still be maintained specified by the calendaring and scheduling system because
   the original "DTSTART" an iCalendar object,
      but MUST only be specified once.

   Description: A value has inherent usage dependencies by other
   properties such as the "RECURRENCE-ID". of "2.0" corresponds to this memo.

   Format Definition: The property is defined by the following notation:

        exrule

         version    = "EXRULE" exrparam "VERSION" verparam ":" recur vervalue CRLF

        exrparam

         verparam   = *(";" xparam)

         vervalue   = "2.0"         ;This memo
                    / maxver
                    / (minver ";" maxver)

         minver     = <A IANA registered iCalendar version identifier>
         ;Minimum iCalendar version needed to parse the iCalendar object

         maxver     = <A IANA registered iCalendar version identifier>
         ;Maximum iCalendar version needed to parse the iCalendar object
   Example: The following are examples is an example of this property.  Except every
   other week, on Tuesday and Thursday for 4 occurrences:

        EXRULE:FREQ=WEEKLY;COUNT=4;INTERVAL=2;BYDAY=TU,TH

   Figure 147
   Except daily for 10 occurrences:

        EXRULE:FREQ=DAILY;COUNT=10

   Except yearly in June and July for 8 occurrences:

        EXRULE:FREQ=YEARLY;COUNT=8;BYMONTH=6,7

8.3.3.  Recurrence Date/Times property:

         VERSION:2.0

3.8.  Component Properties

   The following properties can appear within calendar components, as
   specified by each component property definition.

3.8.1.  Descriptive Component Properties

   The following properties specify descriptive information about
   calendar components.

3.8.1.1.  Attachment

   Property Name: RDATE ATTACH

   Purpose: This The property defines provides the list of date/times for capability to associate a
   recurrence set. document
      object with a calendar component.

   Value Type: The default value type for this property is DATE-TIME. URI.  The
      value type can also be set to DATE or PERIOD. BINARY to indicate inline binary
      encoded content information.

   Property Parameters: Non-standard, inline encoding, format type and
      value data type and time zone
   identifier property parameters can be specified on this
      property.

   Conformance: The property can be specified in a "VEVENT", "VTODO",
      "VJOURNAL" or "VTIMEZONE" "VALARM" calendar components.

   Description: This The property can appear along with the "RRULE" be specified within "VEVENT", "VTODO",
      "VJOURNAL", or "VALARM" calendar components.  This property
   to define an aggregate set of repeating occurrences.  When they both
   appear in can be
      specified multiple times within an iCalendar object, the recurring events are defined by
   the union of occurrences object.

   Format Definition: The property is defined by both the "RDATE" and "RRULE".

   The recurrence dates, if specified, are used in computing the
   recurrence set.  The recurrence set is following notation:

         attach     = "ATTACH" attparam ":" uri  CRLF

         attach     =/ "ATTACH" attparam ";" "ENCODING" "=" "BASE64"
                       ";" "VALUE" "=" "BINARY" ":" binary

         attparam   = *(

                    ; the complete set of recurrence
   instances for a calendar component.  The recurrence set following is generated
   by considering the initial "DTSTART" property along with optional,
                    ; but MUST NOT occur more than once

                    (";" fmttypeparam) /

                    ; the "RRULE",
   "RDATE", "EXDATE" following is optional,
                    ; and "EXRULE" properties contained within the
   iCalendar object. MAY occur more than once

                    (";" xparam)

                    )

   Example: The "DTSTART" following are examples of this property:

         ATTACH:CID:jsmith.part3.960817T083000.xyzMail@host1.com

         ATTACH;FMTTYPE=application/postscript:ftp://xyzCorp.com/pub/
          reports/r-960812.ps

3.8.1.2.  Categories

   Property Name: CATEGORIES

   Purpose: This property defines the first instance
   in the recurrence set.  Multiple instances of the "RRULE" categories for a calendar
      component.

   Value Type: TEXT

   Property Parameters: Non-standard and
   "EXRULE" properties language property parameters
      can also be specified to define more
   sophisticated recurrence sets. on this property.

   Conformance: The final recurrence set property can be specified within "VEVENT", "VTODO"
      or "VJOURNAL" calendar components.

   Description: This property is generated
   by gathering all used to specify categories or subtypes
      of the start date/times generated by any calendar component.  The categories are useful in searching
      for a calendar component of the
   specified "RRULE" and "RDATE" properties, a particular type and excluding any start
   date/times which fall within category.
      Within the union of start date/times generated
   by any specified "EXRULE" and "EXDATE" properties.  This implies that
   start date/times within exclusion related properties (i.e., "EXDATE"
   and "EXRULE") take precedence over those "VEVENT", "VTODO" or "VJOURNAL" calendar components,
      more than one category can be specified by inclusion
   properties (i.e., "RDATE" and "RRULE").  Where duplicate instances
   are generated as a list of categories
      separated by the "RRULE" and "RDATE" properties, only one
   recurrence is considered.  Duplicate instances are ignored. COMMA character (US-ASCII decimal 44).

   Format Definition: The property is defined by the following notation:

        rdate

         categories = "RDATE" rdtparam "CATEGORIES" catparam ":" rdtval text *("," rdtval) text)
                      CRLF

        rdtparam

         catparam   = *(

                    ; the following are is optional,
                    ; but MUST NOT occur more than once

                    (";" "VALUE" "=" ("DATE-TIME" / "DATE" / "PERIOD")) /
                   (";" tzidparam) languageparam ) /

                    ; the following is optional,
                    ; and MAY occur more than once

                    (";" xparam)

                    )

        rdtval     = date-time / date / period
        ;Value MUST match value type

   Example: The following are examples of this property:

        RDATE:19970714T123000Z

        RDATE;TZID=US-EASTERN:19970714T083000

        RDATE;VALUE=PERIOD:19960403T020000Z/19960403T040000Z,
         19960404T010000Z/PT3H

        RDATE;VALUE=DATE:19970101,19970120,19970217,19970421
         19970526,19970704,19970901,19971014,19971128,19971129,19971225

   Figure 151

8.3.4.  Recurrence Identifier Range

   Parameter

         CATEGORIES:APPOINTMENT,EDUCATION

         CATEGORIES:MEETING

3.8.1.3.  Classification

   Property Name: RANGE CLASS

   Purpose: To specify the effective range of recurrence instances from
   the instance specified by This property defines the recurrence identifier access classification for a
      calendar component.

   Value Type: TEXT

   Property Parameters: Non-standard property parameters can be
      specified by the on this property.

   Description:

   Conformance: The parameter property can be specified on a property that
   specifies once in a recurrence identifier.  The parameter specifies "VEVENT",
      "VTODO" or "VJOURNAL" calendar components.

   Description: An access classification is only one component of the
   effective range
      general security system within a calendar application.  It
      provides a method of recurrence instances that is specified by capturing the
   property.  The effective range is from scope of the recurrence identified
   specified by access the property.  If this parameter is not specified
      calendar owner intends for information within an
   allowed property, then the default range individual
      calendar entry.  The access classification of an individual
      iCalendar component is useful when measured along with the single instance
   specified by other
      security components of a calendar system (e.g., calendar user
      authentication, authorization, access rights, access role, etc.).

      Hence, the recurrence identifier value semantics of the property.  The
   parameter value can individual access classifications
      cannot be "THISANDPRIOR" to indicate a range completely defined by this memo alone.  Additionally,
      due to the recurrence identified value "blind" nature of most exchange processes using this
      memo, these access classifications cannot serve as an enforcement
      statement for a system receiving an iCalendar object.  Rather,
      they provide a method for capturing the intention of the calendar
      owner for the access to the calendar component.

   Format Definition: The property and all prior
   instances. is defined by the following notation:

         class      = "CLASS" classparam ":" classvalue CRLF

         classparam = *(";" xparam)

         classvalue = "PUBLIC" / "PRIVATE" / "CONFIDENTIAL" / iana-token
                    / x-name
         ;Default is PUBLIC

   Example: The parameter value can also be "THISANDFUTURE" following is an example of this property:

         CLASS:PUBLIC

3.8.1.4.  Comment

   Property Name: COMMENT

   Purpose: This property specifies non-processing information intended
      to
   indicate provide a range defined by comment to the recurrence identifier calendar user.

   Value Type: TEXT

   Property Parameters: Non-standard, alternate text representation and all
   subsequent instances.
      language property parameters can be specified on this property.

   Conformance: This property can be specified in "VEVENT", "VTODO",
      "VJOURNAL", "VTIMEZONE" or "VFREEBUSY" calendar components.

   Description: The property can be specified multiple times.

   Format Definition: The property parameter is defined by the following

        rangeparam notation:

         comment    = "RANGE" "=" ("THISANDPRIOR" "COMMENT" commparam ":" text CRLF

         commparam  = *(

                    ; To specify all instances prior to the recurrence identifier following are optional,
                    ; but MUST NOT occur more than once

                    (";" altrepparam) / (";" languageparam) / "THISANDFUTURE")

                    ; To specify the instance specified by the recurrence identifier following is optional,
                    ; and all subsequent recurrence instances MAY occur more than once

                    (";" xparam)

                    )

   Example:

        RECURRENCE-ID;RANGE=THISANDPRIOR:19980401T133000Z

   Figure 153

8.3.5.  Recurrence Rule The following is an example of this property:

     COMMENT:The meeting really needs to include both ourselves
       and the customer. We can't hold this meeting without them.
       As a matter of fact\, the venue for the meeting ought to be at
       their site. - - John

3.8.1.5.  Description

   Property Name: RRULE DESCRIPTION

   Purpose: This property defines provides a rule or repeating pattern for
   recurring events, to-dos, or time zone definitions. more complete description of the
      calendar component, than that provided by the "SUMMARY" property.

   Value Type: RECUR TEXT

   Property Parameters: Non-standard Non-standard, alternate text representation and
      language property parameters can be specified on this property.

   Conformance: This The property can be specified one or more times in
   recurring the "VEVENT", "VTODO" and "VTODO",
      "VJOURNAL" or "VALARM" calendar components.  It  The property can also be
      specified once in each STANDARD or DAYLIGHT sub-component
   of the "VTIMEZONE" multiple times only within a "VJOURNAL" calendar
      component.

   Description: The recurrence rule, if specified, This property is used in computing
   the recurrence set.  The recurrence set is the complete set of
   recurrence instances for a calendar component.  The recurrence set is
   generated by considering the initial "DTSTART" property along with the "RRULE", "RDATE", "EXDATE" "VEVENT" and "EXRULE" properties contained
   within "VTODO" to
      capture lengthy textual decriptions associated with the iCalendar object.  The "DTSTART" activity.

      This property defines the
   first instance is used in the recurrence set.  Multiple instances of the
   "RRULE" and "EXRULE" properties can also be specified "VJOURNAL" calendar component to define
      capture one more
   sophisticated recurrence sets.  The final recurrence set textual journal entries.

      This property is generated
   by gathering all of used in the start date/times generated by any "VALARM" calendar component to
      capture the display text for a DISPLAY category of alarm, to
      capture the
   specified "RRULE" and "RDATE" properties, body text for an EMAIL category of alarm and excluding any start
   date/times which fall within to
      capture the union argument string for a PROCEDURE category of start date/times generated alarm.

   Format Definition: The property is defined by any specified "EXRULE" the following notation:

         description        = "DESCRIPTION" descparam ":" text CRLF

         descparam  = *(

                    ; the following are optional,
                    ; but MUST NOT occur more than once

                    (";" altrepparam) / (";" languageparam) /

                    ; the following is optional,
                    ; and "EXDATE" properties. MAY occur more than once

                    (";" xparam)

                    )

   Example: The following is an example of the property with formatted
      line breaks in the property value:

         DESCRIPTION:Meeting to provide technical review for "Phoenix"
           design.\n Happy Face Conference Room. Phoenix design team
           MUST attend this meeting.\n RSVP to team leader.

      The following is an example of the property with folding of long
      lines:

         DESCRIPTION:Last draft of the new novel is to be completed
           for the editor's proof today.

3.8.1.6.  Geographic Position

   Property Name: GEO

   Purpose: This implies that
   start date/times within exclusion property specifies information related properties (i.e., "EXDATE"
   and "EXRULE") take precedence over those to the global
      position for the activity specified by inclusion
   properties (i.e., "RDATE" and "RRULE").  Where duplicate instances
   are generated by the "RRULE" and "RDATE" properties, only one
   recurrence is considered.  Duplicate instances are ignored. a calendar component.

   Value Type: FLOAT.  The "DTSTART" and "DTEND" value MUST be two SEMICOLON separated FLOAT
      values.

   Property Parameters: Non-standard property pair or "DTSTART" and "DURATION" parameters can be
      specified on this property.

   Conformance: This property pair, can be specified within the iCalendar object defines in "VEVENT" or "VTODO"
      calendar components.

   Description: The property value specifies latitude and longitude, in
      that order (i.e., "LAT LON" ordering).  The longitude represents
      the
   first instance location east or west of the recurrence.  When used with prime meridian as a recurrence rule,
   the "DTSTART" positive or
      negative real number, respectively.  The longitude and "DTEND" properties MUST latitude
      values MAY be specified in local time up to six decimal places, which will allow
      for accuracy to within one meter of geographical position.
      Receiving applications MUST accept values of this precision and
      MAY truncate values of greater precision.

      Values for latitude and longitude shall be expressed as decimal
      fractions of degrees.  Whole degrees of latitude shall be
      represented by a two-digit decimal number ranging from 0 through
      90.  Whole degrees of longitude shall be represented by a decimal
      number ranging from 0 through 180.  When a decimal fraction of a
      degree is specified, it shall be separated from the appropriate set whole number
      of "VTIMEZONE" calendar components MUST degrees by a decimal point.

      Latitudes north of the equator shall be
   included.  For detail on specified by a plus sign
      (+), or by the usage absence of a minus sign (-), preceding the "VTIMEZONE" calendar
   component, see digits
      designating degrees.  Latitudes south of the "VTIMEZONE" calendar component definition.

   Any duration associated with Equator shall be
      designated by a minus sign (-) preceding the iCalendar object applies digits designating
      degrees.  A point on the Equator shall be assigned to all
   members the Northern
      Hemisphere.

      Longitudes east of the generated recurrence set.  Any modified duration for
   specific recurrences MUST prime meridian shall be explicitly specified using the "RDATE"
   property.

   Format Definition: This property is defined by a plus
      sign (+), or by the following
   notation:

        rrule      = "RRULE" rrulparam ":" recur CRLF

        rrulparam  = *(";" xparam)

   Example: All examples assume the Eastern United States time zone.

      Daily for 10 occurrences:

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=DAILY;COUNT=10

        ==> (1997 9:00 AM EDT)September 2-11

      Daily until December 24, 1997:

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=DAILY;UNTIL=19971224T000000Z

        ==> (1997 9:00 AM EDT)September 2-30;October 1-25
            (1997 9:00 AM EST)October 26-31;November 1-30;December 1-23

      Every other day - forever:

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=DAILY;INTERVAL=2
        ==> (1997 9:00 AM EDT)September2,4,6,8...24,26,28,30;
             October 2,4,6...20,22,24
            (1997 9:00 AM EST)October 26,28,30;November
            1,3,5,7...25,27,29; Dec 1,3,...

      Every 10 days, 5 occurrences:

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=DAILY;INTERVAL=10;COUNT=5

        ==> (1997 9:00 AM EDT)September 2,12,22;
        October 2,12

      Everyday in January, for 3 years:

        DTSTART;TZID=US-Eastern:19980101T090000
        RRULE:FREQ=YEARLY;UNTIL=20000131T090000Z;
         BYMONTH=1;BYDAY=SU,MO,TU,WE,TH,FR,SA
        or
        RRULE:FREQ=DAILY;UNTIL=20000131T090000Z;
        BYMONTH=1

        ==> (1998 9:00 AM EDT)January 1-31
            (1999 9:00 AM EDT)January 1-31
            (2000 9:00 AM EDT)January 1-31

      Weekly for 10 occurrences

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=WEEKLY;COUNT=10

        ==> (1997 9:00 AM EDT)September 2,9,16,23,30;
        October 7,14,21
            (1997 9:00 AM EST)October 28;November 4
      Weekly until December 24, 1997

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=WEEKLY;UNTIL=19971224T000000Z

        ==> (1997 9:00 AM EDT)September 2,9,16,23,30;
        October 7,14,21(1997 9:00 AM EST)October 28;
        November 4,11,18,25;
        December 2,9,16,23

      Every other week - forever:

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=WEEKLY;INTERVAL=2;WKST=SU

        ==> (1997 9:00 AM EDT)September 2,16,30;October 14
            (1997 9:00 AM EST)October 28;November 11,25;
            December 9,23(1998 9:00 AM EST)January 6,20;February
        ...

      Weekly on Tuesday and Thursday for 5 weeks:

       DTSTART;TZID=US-Eastern:19970902T090000
       RRULE:FREQ=WEEKLY;UNTIL=19971007T000000Z;
       WKST=SU;BYDAY=TU,TH

       or

       RRULE:FREQ=WEEKLY;COUNT=10;WKST=SU;BYDAY=TU,TH

       ==> (1997 9:00 AM EDT)September 2,4,9,11,16,18,23,25,30;
       October 2

      Every other week on Monday, Wednesday and Friday until
      December 24, 1997, but starting on Tuesday,
      September 2, 1997:

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=WEEKLY;INTERVAL=2;UNTIL=19971224T000000Z;
        WKST=SU;BYDAY=MO,WE,FR
        ==> (1997 9:00 AM EDT)September 2,3,5,15,17,19,29;October
        1,3,13,15,17
            (1997 9:00 AM EST)October 27,29,31;
            November 10,12,14,24,26,28;
            December 8,10,12,22
      Every other week on Tuesday and Thursday, for 8 occurrences:

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=8;WKST=SU;
        BYDAY=TU,TH

        ==> (1997 9:00 AM EDT)September 2,4,16,18,30;
        October 2,14,16

      Monthly on the 1st Friday for ten occurrences:

        DTSTART;TZID=US-Eastern:19970905T090000
        RRULE:FREQ=MONTHLY;COUNT=10;BYDAY=1FR

        ==> (1997 9:00 AM EDT)September 5;October 3
            (1997 9:00 AM EST)November 7;Dec 5
            (1998 9:00 AM EST)January 2;February 6;
            March 6;April 3
            (1998 9:00 AM EDT)May 1;June 5

      Monthly on the 1st Friday until December 24, 1997:

        DTSTART;TZID=US-Eastern:19970905T090000
        RRULE:FREQ=MONTHLY;UNTIL=19971224T000000Z;
        BYDAY=1FR

        ==> (1997 9:00 AM EDT)September 5;October 3
            (1997 9:00 AM EST)November 7;December 5

      Every other month on absence of a minus sign (-), preceding the 1st and last Sunday
      digits designating degrees.  Longitudes west of the month for 10
      occurrences:

        DTSTART;TZID=US-Eastern:19970907T090000
        RRULE:FREQ=MONTHLY;INTERVAL=2;COUNT=10;
        BYDAY=1SU,-1SU

        ==> (1997 9:00 AM EDT)September 7,28
            (1997 9:00 AM EST)November 2,30

            (1998 9:00 AM EST)January 4,25;March 1,29
            (1998 9:00 AM EDT)May 3,31
      Monthly meridian shall
      be designated by minus sign (-) preceding the digits designating
      degrees.  A point on the second prime meridian shall be assigned to last Monday of the month for 6 months:

        DTSTART;TZID=US-Eastern:19970922T090000
        RRULE:FREQ=MONTHLY;COUNT=6;BYDAY=-2MO

        ==> (1997 9:00 AM EDT)September 22;October 20
            (1997 9:00 AM EST)November 17;December 22
            (1998 9:00 AM EST)January 19;February 16

      Monthly
      Eastern Hemisphere.  A point on the third 180th meridian shall be
      assigned to the Western Hemisphere.  One exception to this last day of the month, forever:

        DTSTART;TZID=US-Eastern:19970928T090000
        RRULE:FREQ=MONTHLY;BYMONTHDAY=-3

        ==> (1997 9:00 AM EDT)September 28
            (1997 9:00 AM EST)October 29;November 28;
            December 29(1998 9:00 AM EST)January 29;
            February 26
        ...

      Monthly on
      convention is permitted.  For the 2nd and 15th special condition of describing
      a band of latitude around the month for 10 occurrences:

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=2,15

        ==> (1997 9:00 AM EDT)September 2,15;October 2,15
            (1997 9:00 AM EST)November 2,15;December 2,15
            (1998 9:00 AM EST)January 2,15

      Monthly on earth, the first and last day East Bounding Coordinate
      data element shall be assigned the value +180 (180) degrees.

      Any spatial address with a latitude of +90 (90) or -90 degrees
      will specify the month for 10 occurrences:

        DTSTART;TZID=US-Eastern:19970930T090000
        RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=1,-1

        ==> (1997 9:00 AM EDT)September 30;October 1
            (1997 9:00 AM EST)October 31;November 1,30;
            December 1,31(1998 9:00 AM EST)January 1,31;
            February 1
      Every 18 months on position at the 10th thru 15th North or South Pole,
      respectively.  The component for longitude may have any legal
      value.

      With the exception of the month for 10
      occurrences:

        DTSTART;TZID=US-Eastern:19970910T090000
        RRULE:FREQ=MONTHLY;INTERVAL=18;COUNT=10;
        BYMONTHDAY=10,11,12,13,14,
         15

        ==> (1997 9:00 AM EDT)September 10,11,12,13,14,15

            (1999 9:00 AM EST)March 10,11,12,13

      Every Tuesday, every other month:

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=MONTHLY;INTERVAL=2;BYDAY=TU

        ==> (1997 9:00 AM EDT)September 2,9,16,23,30
            (1997 9:00 AM EST)November 4,11,18,25
            (1998 9:00 AM EST)January 6,13,20,27;
            March 3,10,17,24,31
        ...

      Yearly special condition described above, this
      form is specified in June and July Department of Commerce, 1986, Representation
      of geographic point locations for 10 occurrences:

        DTSTART;TZID=US-Eastern:19970610T090000

   RRULE:FREQ=YEARLY;COUNT=10;BYMONTH=6,7
        ==> (1997 9:00 AM EDT)June 10;July 10
            (1998 9:00 AM EDT)June 10;July 10
            (1999 9:00 AM EDT)June 10;July 10
            (2000 9:00 AM EDT)June 10;July 10
            (2001 9:00 AM EDT)June 10;July 10
        Note: Since none information interchange (Federal
      Information Processing Standard 70-1): Washington, Department of
      Commerce, National Institute of Standards and Technology.

      The simple formula for converting degrees-minutes-seconds into
      decimal degrees is:

      decimal = degrees + minutes/60 + seconds/3600.

   Format Definition: The property is defined by the BYDAY, BYMONTHDAY or
        BYYEARDAY following notation:

         geo        = "GEO" geoparam ":" geovalue CRLF

         geoparam   = *(";" xparam)

         geovalue   = float ";" float
         ;Latitude and Longitude components are specified, the day

   Example: The following is
        gotten from DTSTART
      Every other year on January, February, and March an example of this property:

         GEO:37.386013;-122.082932

3.8.1.7.  Location

   Property Name: LOCATION

   Purpose: The property defines the intended venue for 10 occurrences:

        DTSTART;TZID=US-Eastern:19970310T090000
        RRULE:FREQ=YEARLY;INTERVAL=2;COUNT=10;
        BYMONTH=1,2,3

        ==> (1997 9:00 AM EST)March 10
            (1999 9:00 AM EST)January 10;February 10;March 10
            (2001 9:00 AM EST)January 10;February 10;March 10
            (2003 9:00 AM EST)January 10;February 10;March 10

      Every 3rd year on the 1st, 100th activity
      defined by a calendar component.

   Value Type: TEXT

   Property Parameters: Non-standard, alternate text representation and 200th day
      for 10 occurrences:

        DTSTART;TZID=US-Eastern:19970101T090000
        RRULE:FREQ=YEARLY;INTERVAL=3;COUNT=10;
        BYYEARDAY=1,100,200

        ==> (1997 9:00 AM EST)January 1
            (1997 9:00 AM EDT)April 10;July 19
            (2000 9:00 AM EST)January 1
            (2000 9:00 AM EDT)April 9;July 18
            (2003 9:00 AM EST)January 1
            (2003 9:00 AM EDT)April 10;July 19
            (2006 9:00 AM EST)January 1

      Every 20th Monday
      language property parameters can be specified on this property.

   Conformance: This property can be specified in "VEVENT" or "VTODO"
      calendar component.

   Description: Specific venues such as conference or meeting rooms may
      be explicitly specified using this property.  An alternate
      representation may be specified that is a URI that points to
      directory information with more structured specification of the year, forever:

        DTSTART;TZID=US-Eastern:19970519T090000
        RRULE:FREQ=YEARLY;BYDAY=20MO

        ==> (1997 9:00 AM EDT)May 19
            (1998 9:00 AM EDT)May 18
            (1999 9:00 AM EDT)May 17
        ...

      Monday of week number 20 (where
      location.  For example, the default start
      of alternate representation may specify
      either an LDAP URI pointing to an LDAP server entry or a CID URI
      pointing to a MIME body part containing a vCard [RFC2426] for the week is Monday), forever:

        DTSTART;TZID=US-Eastern:19970512T090000
        RRULE:FREQ=YEARLY;BYWEEKNO=20;BYDAY=MO

        ==> (1997 9:00 AM EDT)May 12
            (1998 9:00 AM EDT)May 11
            (1999 9:00 AM EDT)May 17
        ...

      Every Thursday in March, forever:

        DTSTART;TZID=US-Eastern:19970313T090000
        RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=TH

        ==> (1997 9:00 AM EST)March 13,20,27
            (1998 9:00 AM EST)March 5,12,19,26
            (1999 9:00 AM EST)March 4,11,18,25
        ...

      Every Thursday, but only during June, July, and August,
       forever:

        DTSTART;TZID=US-Eastern:19970605T090000
        RRULE:FREQ=YEARLY;BYDAY=TH;BYMONTH=6,7,8

        ==> (1997 9:00 AM EDT)June 5,12,19,26;July 3,10,17,24,31;
                          August 7,14,21,28
            (1998 9:00 AM EDT)June 4,11,18,25;July 2,9,16,23,30;
                          August 6,13,20,27
            (1999 9:00 AM EDT)June 3,10,17,24;July 1,8,15,22,29;
                          August 5,12,19,26
        ...

      Every Friday the 13th, forever:

        DTSTART;TZID=US-Eastern:19970902T090000
        EXDATE;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=MONTHLY;BYDAY=FR;BYMONTHDAY=13

        ==> (1998 9:00 AM EST)February 13;March 13;
        November 13(1999 9:00 AM EDT)August 13
            (2000 9:00 AM EDT)October 13
        ...

      The first Saturday that follows the first Sunday of the month,
       forever:

        DTSTART;TZID=US-Eastern:19970913T090000
        RRULE:FREQ=MONTHLY;BYDAY=SA;
        BYMONTHDAY=7,8,9,10,11,12,13

        ==> (1997 9:00 AM EDT)September 13;October 11
            (1997 9:00 AM EST)November 8;December 13
            (1998 9:00 AM EST)January 10;February 7;March 7
            (1998 9:00 AM EDT)April 11;May 9;June 13...
        ...

      Every four years, the first Tuesday after a Monday in November,
      forever (U.S. Presidential Election day):

        DTSTART;TZID=US-Eastern:19961105T090000
        RRULE:FREQ=YEARLY;INTERVAL=4;BYMONTH=11;
        BYDAY=TU;BYMONTHDAY=2,3,4,
         5,6,7,8

        ==> (1996 9:00 AM EST)November 5
            (2000 9:00 AM EST)November 7
            (2004 9:00 AM EST)November 2
        ...

      The 3rd instance into the month of one of Tuesday, Wednesday or
      Thursday, for the next 3 months:

        DTSTART;TZID=US-Eastern:19970904T090000
        RRULE:FREQ=MONTHLY;COUNT=3;BYDAY=TU,WE,TH;
        BYSETPOS=3

        ==> (1997 9:00 AM EDT)September 4;October 7
            (1997 9:00 AM EST)November 6

      The 2nd to last weekday of the month:

        DTSTART;TZID=US-Eastern:19970929T090000
        RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;
        BYSETPOS=-2

        ==> (1997 9:00 AM EDT)September 29
            (1997 9:00 AM EST)October 30;November 27;December 30
            (1998 9:00 AM EST)January 29;February 26;March 30
        ...

      Every 3 hours from 9:00 AM to 5:00 PM on a specific day:

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=HOURLY;INTERVAL=3;UNTIL=19970902T170000Z

        ==> (September 2, 1997 EDT)09:00,12:00,15:00

      Every 15 minutes for 6 occurrences:

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=MINUTELY;INTERVAL=15;COUNT=6

        ==> (September 2, 1997 EDT)09:00,09:15,09:30,09:45,10:00,10:15

      Every hour and a half for 4 occurrences:

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=MINUTELY;INTERVAL=90;COUNT=4

        ==> (September 2, 1997 EDT)09:00,10:30;12:00;13:30

      Every 20 minutes from 9:00 AM to 4:40 PM every day:

        DTSTART;TZID=US-Eastern:19970902T090000
        RRULE:FREQ=DAILY;BYHOUR=9,10,11,12,13,14,15,16;BYMINUTE=0,20,40
        or
        RRULE:FREQ=MINUTELY;INTERVAL=20;BYHOUR=9,10,11,12,13,14,15,16

        ==> (September 2, 1997 EDT)9:00,9:20,9:40,10:00,10:20,
                                   ... 16:00,16:20,16:40
            (September 3, 1997 EDT)9:00,9:20,9:40,10:00,10:20,
                                  ...16:00,16:20,16:40
        ...

      An example where the days generated makes a difference because of
      WKST:

        DTSTART;TZID=US-Eastern:19970805T090000
        RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=MO
        ==> (1997 EDT)Aug 5,10,19,24

        changing only WKST from MO to SU, yields different results...

        DTSTART;TZID=US-Eastern:19970805T090000
        RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=SU
        ==> (1997 EDT)August 5,17,19,31

8.4.  Alarm Component Properties

   The following properties specify alarm information in calendar
   components.

8.4.1.  Action

   Property Name: ACTION

   Purpose: This property defines the action to be invoked when an alarm
   is triggered.

   Value Type: TEXT

   Property Parameters: Non-standard property parameters can be
   specified on this property.

   Conformance: This property MUST be specified once in a "VALARM"
   calendar component.

   Description: Each "VALARM" calendar component has a particular type
   of action associated with it.  This property specifies the type of
   action

   Format Definition: The property
      location.

   Format Definition: The property is defined by the following notation:

        action

         location   = "ACTION" actionparam "LOCATION locparam ":" actionvalue text CRLF

        actionparam        = *(";" xparam)

        actionvalue

         locparam   = "AUDIO" / "DISPLAY" / "EMAIL" / "PROCEDURE" *(

                    ; the following are optional,
                    ; but MUST NOT occur more than once

                    (";" altrepparam) / iana-token (";" languageparam) / x-name

                    ; the following is optional,
                    ; and MAY occur more than once

                    (";" xparam)

                    )

   Example: The following are some examples of this property in a "VALARM"
   calendar component:

        ACTION:AUDIO

        ACTION:DISPLAY

        ACTION:PROCEDURE

8.4.2.  Alarm Repeat Count property:

         LOCATION:Conference Room - F123, Bldg. 002

         LOCATION;ALTREP="http://xyzcorp.com/conf-rooms/f123.vcf":
          Conference Room - F123, Bldg. 002

3.8.1.8.  Percent Complete

   Property Name: REPEAT PERCENT-COMPLETE

   Purpose: This property defines the number is used by an assignee or delegatee of time a to-do
      to convey the alarm should be
   repeated, after percent completion of a to-do to the initial trigger. Organizer.

   Value Type: INTEGER

   Property Parameters: Non-standard property parameters can be
      specified on this property.

   Conformance: This property can be specified in a "VALARM" "VTODO" calendar
      component.

   Description: If The property value is a positive integer between zero
      and one hundred.  A value of "0" indicates the to-do has not yet
      been started.  A value of "100" indicates that the to-do has been
      completed.  Integer values in between indicate the percent
      partially complete.

      When a to-do is assigned to multiple individuals, the alarm triggers more than once, then this property
   MUST be specified along
      value indicates the percent complete for that portion of the to-do
      assigned to the assignee or delegatee.  For example, if a to-do is
      assigned to both individuals "A" and "B".  A reply from "A" with a
      percent complete of "70" indicates that "A" has completed 70% of
      the "DURATION" property. to-do assigned to them.  A reply from "B" with a percent
      complete of "50" indicates "B" has completed 50% of the to-do
      assigned to them.

   Format Definition: The property is defined by the following notation:

        repeatcnt

         percent = "REPEAT" repparam "PERCENT-COMPLETE" pctparam ":" integer CRLF
        ;Default is "0", zero.

        repparam

         pctparam   = *(";" xparam)

   Example: The following is an example of this property for an alarm
   that repeats 4 additional times with a 5 minute delay after the
   initial triggering of the alarm:

        REPEAT:4
        DURATION:PT5M

8.4.3.  Alarm Trigger to show 39%
      completion:

         PERCENT-COMPLETE:39

3.8.1.9.  Priority

   Property Name: TRIGGER PRIORITY

   Purpose: This property specifies when an alarm will trigger.

   Value Type: The default value type is DURATION. The value type can
   be set to a DATE-TIME value type, in which case property defines the value MUST
   specify relative priority for a UTC formatted DATE-TIME value. calendar
      component.

   Value Type: INTEGER

   Property Parameters: Non-standard, value data type, time zone
   identifier or trigger relationship Non-standard property parameters can be
      specified on this property.  The trigger relationship property
   parameter MUST only be specified when the value type is DURATION.

   Conformance: This The property MUST can be specified in the "VALARM" a "VEVENT" or "VTODO"
      calendar component.

   Description: Within the "VALARM" calendar component, this property
   defines when the alarm will trigger.  The default value type is
   DURATION, specifying a relative time for the trigger of the alarm. The default duration priority is relative to the start of specified as an event or to-do
   that integer in the alarm is associated with.  The duration can be explicitly
   set range
      zero to trigger from either the end or the start of the associated
   event or to-do with the "RELATED" parameter. nine.  A value of START will
   set the alarm to trigger off the start of the associated event or
   to-do. zero (US-ASCII decimal 48) specifies an
      undefined priority.  A value of END will set the alarm to trigger off one (US-ASCII decimal 49) is the end
      highest priority.  A value of
   the associated event or to-do.

   Either a positive or negative duration may be specified for the
   "TRIGGER" property.  An alarm with a positive duration two (US-ASCII decimal 50) is triggered
   after the associated start or end
      second highest priority.  Subsequent numbers specify a decreasing
      ordinal priority.  A value of nine (US-ASCII decimal 58) is the event or to-do.  An alarm
      lowest priority.

      A CUA with a negative duration is triggered before the associated start or
   end three-level priority scheme of the event or to-do.

   The "RELATED" property parameter "HIGH", "MEDIUM" and
      "LOW" is not valid if the value type of
   the mapped into this property is set to DATE-TIME (i.e., for an absolute date and time
   alarm trigger).  If such that a value type of DATE-TIME is specified, then the property value MUST be specified in
      the UTC time format.  If an
   absolute trigger is specified on an alarm for a recurring event or
   to-do, then range of one (US-ASCII decimal 49) to four (US-ASCII decimal
      52) specifies "HIGH" priority.  A value of five (US-ASCII decimal
      53) is the alarm will only trigger for normal or "MEDIUM" priority.  A value in the specified absolute
   date/time, along range of
      six (US- ASCII decimal 54) to nine (US-ASCII decimal 58) is "LOW"
      priority.

      A CUA with any specified repeating instances.

   If the trigger a priority schema of "A1", "A2", "A3", "B1", "B2", ...,
      "C3" is set relative mapped into this property such that a property value of
      one (US-ASCII decimal 49) specifies "A1", a property value of two
      (US- ASCII decimal 50) specifies "A2", a property value of three
      (US-ASCII decimal 51) specifies "A3", and so forth up to START, then a
      property value of 9 (US-ASCII decimal 58) specifies "C3".

      Other integer values are reserved for future use.

      Within a "VEVENT" calendar component, this property specifies a
      priority for the "DTSTART" event.  This property
   MUST may be present in the associated "VEVENT" or useful when more
      than one event is scheduled for a given time period.

      Within a "VTODO" calendar
   component.  If an alarm is component, this property specified a
      priority for an event with the trigger
   set relative to the END, then the "DTEND" to-do.  This property or is useful in prioritizing
      multiple action items for a given time period.

   Format Definition: The property is defined by the "DSTART"
   and "DURATION' properties MUST following notation:

         priority   = "PRIORITY" prioparam ":" privalue CRLF
         ;Default is zero

         prioparam  = *(";" xparam)

         privalue   = integer       ;Must be present in the associated "VEVENT"
   calendar component.  If range [0..9]
            ; All other values are reserved for future use

      The following is an example of a property with the alarm highest
      priority:

         PRIORITY:1

      The following is specified for an example of a to-do property with a
   trigger set relative next highest
      priority:

         PRIORITY:2

   Example: The following is an example of a property with no priority.

      This is equivalent to not specifying the END, then either the "DUE" "PRIORITY" property:

         PRIORITY:0

3.8.1.10.  Resources

   Property Name: RESOURCES

   Purpose: This property or defines the "DSTART" equipment or resources anticipated
      for an activity specified by a calendar entity..

   Value Type: TEXT

   Property Parameters: Non-standard, alternate text representation and "DURATION' properties MUST
      language property parameters can be present specified on this property.

   Conformance: This property can be specified in the
   associated "VEVENT" or "VTODO"
      calendar component.

   Alarms specified in an event or to-do which is defined in terms of a
   DATE

   Description: The property value type will is an arbitrary text.  More than one
      resource can be triggered relative to 00:00:00 UTC on the specified date.  For example, if "DTSTART:19980205, then as a list of resources separated by the duration
   trigger will be relative to19980205T000000Z.
      COMMA character (US-ASCII decimal 44).

   Format Definition: The property is defined by the following notation:

        trigger

         resources  = "TRIGGER" (trigrel / trigabs)

        trigrel "RESOURCES" resrcparam ":" text *("," text) CRLF

         resrcparam = *(

                    ; the following are optional,
                    ; but MUST NOT occur more than once

                    (";" "VALUE" "=" "DURATION") altrepparam) / (";" trigrelparam) languageparam) /

                    ; the following is optional,
                    ; and MAY occur more than once

                    (";" xparam)

                    ) ":"  dur-value

        trigabs    = 1*(

                   ; the following is REQUIRED,
                   ; but MUST NOT occur more than once

                     (";" "VALUE" "=" "DATE-TIME") /

                   ; the

   Example: The following is optional,
                   ; and MAY occur more than once

                     (";" xparam)

                     ) ":" date-time

   Example: A trigger set 15 minutes prior to the start an example of the event or
   to-do.

        TRIGGER:-P15M

   A trigger set 5 minutes after the end of the event or to-do.

        TRIGGER;RELATED=END:P5M
   A trigger set to an absolute date/time.

        TRIGGER;VALUE=DATE-TIME:19980101T050000Z

8.5.  Alarm Trigger Relationship

   Parameter Name: RELATED

   Purpose: To specify the relationship of the alarm trigger with
   respect to the start or end of the calendar component.

   Description: The parameter can be specified on properties that
   specify an alarm trigger with a DURATION value type.  The parameter
   specifies whether the alarm will trigger relative to the start or end
   of the calendar component.  The parameter value START will set the
   alarm to trigger off the start of the calendar component; the
   parameter value END will set the alarm to trigger off the end of the
   calendar component.  If the parameter is not specified on an
   allowable property, then the default is START.

   Format Definition: The property parameter is defined by the following
   notation:

        trigrelparam       = "RELATED" "="
                            ("START"       ; Trigger off of start
                           / "END")        ; Trigger off of end

   Example:

        TRIGGER;RELATED=END:PT5M

   Figure 202

8.6.  Change Management Component Properties

   The following properties specify change management information in
   calendar components.

8.6.1.  Date/Time Created this property:

         RESOURCES:EASEL,PROJECTOR,VCR

         RESOURCES;LANGUAGE=fr:1 raton-laveur

3.8.1.11.  Status
   Property Name: CREATED STATUS

   Purpose: This property specifies the date and time that the calendar
   information was created by the calendar user agent in the calendar
   store.

   Note: This is analogous to defines the creation date and time overall status or confirmation for a file in
      the file system. calendar component.

   Value Type: DATE-TIME TEXT

   Property Parameters: Non-standard property parameters can be
      specified on this property.

   Conformance: The This property can be specified once in "VEVENT", "VTODO" or
      "VJOURNAL" calendar components.

   Description: The date and time In a group scheduled calendar component, the property is
      used by the "Organizer" to provide a UTC value. confirmation of the event to
      the "Attendees".  For example in a "VEVENT" calendar component,
      the "Organizer" can indicate that a meeting is tentative,
      confirmed or cancelled.  In a "VTODO" calendar component, the
      "Organizer" can indicate that an action item needs action, is
      completed, is in process or being worked on, or has been
      cancelled.  In a "VJOURNAL" calendar component, the "Organizer"
      can indicate that a journal entry is draft, final or has been
      cancelled or removed.

   Format Definition: The property is defined by the following notation:

        created

     status     = "CREATED" creaparam "STATUS" statparam] ":" date-time statvalue CRLF

        creaparam

     statparam  = *(";" xparam)

     statvalue  = "TENTATIVE"           ;Indicates event is
                                        ;tentative.
                / "CONFIRMED"           ;Indicates event is
                                        ;definite.
                / "CANCELLED"           ;Indicates event was
                                        ;cancelled.
        ;Status values for a "VEVENT"

     statvalue  =/ "NEEDS-ACTION"       ;Indicates to-do needs action.
                / "COMPLETED"           ;Indicates to-do completed.
                / "IN-PROCESS"          ;Indicates to-do in process of
                / "CANCELLED"           ;Indicates to-do was cancelled.
        ;Status values for "VTODO".

     statvalue  =/ "DRAFT"              ;Indicates journal is draft.
                / "FINAL"               ;Indicates journal is final.
                / "CANCELLED"           ;Indicates journal is removed.
        ;Status values for "VJOURNAL".

   Example: The following is an example of this property:

        CREATED:19960329T133000Z

   Figure 204

8.6.2.  Date/Time Stamp property for a "VEVENT"
      calendar component:

         STATUS:TENTATIVE

      The following is an example of this property for a "VTODO"
      calendar component:

         STATUS:NEEDS-ACTION

      The following is an example of this property for a "VJOURNAL"
      calendar component:

         STATUS:DRAFT

3.8.1.12.  Summary

   Property Name: DTSTAMP SUMMARY

   Purpose: The This property indicates the date/time that the instance of defines a short summary or subject for the iCalendar object was created.
      calendar component.

   Value Type: DATE-TIME TEXT

   Property Parameters: Non-standard Non-standard, alternate text representation and
      language property parameters can be specified on this property.

   Conformance: This The property MUST can be included specified in the "VEVENT", "VTODO",
      "VJOURNAL" or "VFREEBUSY" "VALARM" calendar components.

   Description: The value MUST be specified in the UTC time format. This property is also useful to protocols such as [IMIP] that have
   inherent latency issues with the delivery of content.  This property
   will assist used in the proper sequencing of messages containing iCalendar
   objects. "VEVENT", "VTODO" and
      "VJOURNAL" calendar components to capture a short, one line
      summary about the activity or journal entry.

      This property is different than the "CREATED" and "LAST-MODIFIED"
   properties.  These two properties are used to specify when the
   particular calendar data in the "VALARM" calendar store was created and last
   modified.  This is different than when component to
      capture the iCalendar object
   representation subject of the calendar service information was created or
   last modified. an EMAIL category of alarm.

   Format Definition: The property is defined by the following notation:

        dtstamp

         summary    = "DTSTAMP" stmparam "SUMMARY" summparam ":" date-time text CRLF

        stmparam

         summparam  = *(";" *(

                    ; the following are optional,
                    ; but MUST NOT occur more than once

                    (";" altrepparam) / (";" languageparam) /

                    ; the following is optional,
                    ; and MAY occur more than once

                    (";" xparam)

                    )

   Example:

        DTSTAMP:19971210T080000Z

   Figure 206

8.6.3.  Last Modified

   Property Name: LAST-MODIFIED

   Purpose: The property specifies the following is an example of this property:

         SUMMARY:Department Party

3.8.2.  Date and Time Component Properties

   The following properties specify date and time that the related information associated with the calendar component was last revised in the
   calendar store.

   Note: components.

3.8.2.1.  Date/Time Completed

   Property Name: COMPLETED

   Purpose: This is analogous to property defines the modification date and time for that a file
   in the file system. to-do was
      actually completed.

   Value Type: DATE-TIME

   Property Parameters: Non-standard property parameters can be
      specified on this property.

   Conformance: This The property can be specified in the "EVENT", "VTODO",
   "VJOURNAL" or "VTIMEZONE" a "VTODO" calendar components.
      component.

   Description: The property value date and time MUST be specified in the a UTC time format.

   Format Definition: The property is defined by the following notation:

        last-mod

         completed  = "LAST-MODIFIED" lstparam "COMPLETED" compparam ":" date-time CRLF

        lstparam

         compparam  = *(";" xparam)
   Example: The following is are examples an example of this property:

        LAST-MODIFIED:19960817T133000Z

   Figure 208

8.6.4.  Sequence Number

         COMPLETED:19960401T235959Z

3.8.2.2.  Date/Time End

   Property Name: SEQUENCE DTEND

   Purpose: This property defines the revision sequence number of specifies the date and time that a calendar
      component within a sequence of revisions. ends.

   Value Type: integer The default value type is DATE-TIME.  The value type can
      be set to a DATE value type.

   Property Parameters: Non-standard Non-standard, value data type, time zone
      identifier property parameters can be specified on this property.

   Conformance: The This property can be specified in "VEVENT", "VTODO" "VEVENT" or
   "VJOURNAL"
      "VFREEBUSY" calendar component. components.

   Description: When a calendar component is created, its sequence
   number is zero (US-ASCII decimal 48).  It is monotonically
   incremented by the "Organizer's" CUA each time the "Organizer" makes
   a significant revision to Within the "VEVENT" calendar component.  When the
   "Organizer" makes changes to one of the following properties, component, this property
      defines the
   sequence number MUST be incremented: .  "DTSTART" .  "DTEND" .  "DUE"
   .  "RDATE" .  "RRULE" .  "EXDATE" .  "EXRULE" .  "STATUS"

   In addition, changes made date and time by which the "Organizer" to other properties can
   also force the sequence number to be incremented. event ends.  The "Organizer"
   CUA value MUST increment the sequence number when ever it makes changes to
   properties
      be later in time than the calendar component that the "Organizer" deems will
   jeopardize the validity value of the participation status of "DTSTART" property.

      Within the
   "Attendees".  For example, changing "VFREEBUSY" calendar component, this property defines
      the location of a meeting from
   one locale to another distant locale could effectively impact end date and time for the
   participation status of free or busy time information.  The
      time MUST be specified in the "Attendees". UTC time format.  The "Organizer" includes this property value MUST be
      later in an iCalendar object that it
   sends to an "Attendee" to specify time than the current version value of the calendar
   component. "DTSTART" property.

   Format Definition: The "Attendee" includes this property in an iCalendar object that it
   sends to the "Organizer" to specify the version of the calendar
   component that the "Attendee" is referring to.

   A change to the sequence number is not the mechanism that an
   "Organizer" uses to request a response from the "Attendees".  The
   "RSVP" parameter on the "ATTENDEE" property is used by the
   "Organizer" to indicate that a response from the "Attendees" is
   requested.

   Format Definition: This property is defined by the following notation:

        seq

         dtend      = "SEQUENCE" seqparam ":" integer "DTEND" dtendparam":" dtendval CRLF

         dtendparam = *(

                    ; Default the following are optional,
                    ; but MUST NOT occur more than once

                    (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
                    (";" tzidparam) /

                    ; the following is "0"

        seqparam   = *(";" optional,
                    ; and MAY occur more than once

                    (";" xparam)

                    )

         dtendval   = date-time / date
         ;Value MUST match value type

   Example: The following is an example of this property:

         DTEND:19960401T235959Z

         DTEND;VALUE=DATE:19980704

3.8.2.3.  Date/Time Due

   Property Name: DUE

   Purpose: This property for a calendar
   component that was just created by defines the "Organizer".

        SEQUENCE:0

   The following is an example of this property for a calendar component date and time that has been revised two different times by the "Organizer".

        SEQUENCE:2

8.7.  Miscellaneous Component Properties

   The following properties specify information about a number of
   miscellaneous features of calendar components.

8.7.1.  RSVP Expectation

   Parameter Name: RSVP

   Purpose: To specify whether there to-do is an expectation of a favor of
      expected to be completed.

   Value Type: The default value type is DATE-TIME.  The value type can
      be set to a
   reply from the calendar user specified by the DATE value type.

   Property Parameters: Non-standard, value data type, time zone
      identifier property value.

   Description: This parameter parameters can be specified on properties with a
   CAL-ADDRESS value type. this property.

   Conformance: The parameter identifies the expectation of
   a reply from the calendar user specified by the property value.  This
   parameter is used by the "Organizer" to request can be specified once in a participation
   status reply from an "Attendee" of "VTODO" calendar
      component.

   Description: The value MUST be a group scheduled event date/time equal to or to-do.
   If not specified on a property that allows this parameter, after the
   default value is FALSE.
      DTSTART value, if specified.

   Format Definition: The property parameter is defined by the following notation:

        rsvpparam

         due        = "RSVP" "DUE" dueparam":" dueval CRLF

         dueparam   = *(
                    ; the following are optional,
                    ; but MUST NOT occur more than once

                    (";" "VALUE" "=" ("TRUE" ("DATE-TIME" / "DATE")) /
                    (";" tzidparam) / "FALSE")

                    ; Default the following is FALSE optional,
                    ; and MAY occur more than once

                    *(";" xparam)

                    )

         dueval     = date-time / date
         ;Value MUST match value type

   Example:

        ATTENDEE;RSVP=TRUE:MAILTO:jsmith@host.com

   Figure 213

8.7.2.  Language

   Parameter The following is an example of this property:

         DUE:19980430T235959Z

3.8.2.4.  Date/Time Start

   Property Name: LANGUAGE DTSTART

   Purpose: To specify This property specifies when the language calendar component begins.

   Value Type: The default value type is DATE-TIME.  The time value MUST
      be one of the forms defined for text values in the DATE-TIME value type.  The
      value type can be set to a DATE value type.

   Property Parameters: Non-standard, value data type, time zone
      identifier property or
   property parameter.

   Description: This parameter parameters can be specified on properties with a
   text value type.  The parameter identifies the language of the text this property.

   Conformance: This property can be specified in the property "VEVENT", "VTODO",
      "VFREEBUSY", or property parameter value.  The value of "VTIMEZONE" calendar components.

   Description: Within the
   "language" "VEVENT" calendar component, this property parameter is that defined in [RFC 1766].

   For transport
      defines the start date and time for the event.  The property is
      REQUIRED in "VEVENT" calendar components.  Events can have a MIME entity, start
      date/time but no end date/time.  In that case, the Content-Language header field can
   be used to set event does not
      take up any time.

      Within the default language "VFREEBUSY" calendar component, this property defines
      the start date and time for the entire body part.
   Otherwise, no default language free or busy time information.
      The time MUST be specified in UTC time.

      Within the "VTIMEZONE" calendar component, this property defines
      the effective start date and time for a time zone specification.
      This property is assumed. REQUIRED within each STANDARD and DAYLIGHT part
      included in "VTIMEZONE" calendar components and MUST be specified
      as a local DATE-TIME without the "TZID" property parameter.

   Format Definition: The property parameter is defined by the following notation:

        languageparam

         dtstart    =    "LANGUAGE" "DTSTART" dtstparam ":" dtstval CRLF

         dtstparam  = *(

                    ; the following are optional,
                    ; but MUST NOT occur more than once

                    (";" "VALUE" "=" language

        language ("DATE-TIME" / "DATE")) /
                    (";" tzidparam) /

                    ; the following is optional,
                    ; and MAY occur more than once

                      *(";" xparam)

                    )

         dtstval    = <Text identifying a language, as defined in
         [RFC 1766]> date-time / date
         ;Value MUST match value type

   Example:

        SUMMARY;LANGUAGE=us-EN:Company Holiday Party

        LOCATION;LANGUAGE=en:Germany
        LOCATION;LANGUAGE=no:Tyskland The following is an example makes use of the Quoted-Printable
      encoding in order to represent non-ASCII characters.

        LOCATION;LANGUAGE=da:K=C3=B8benhavn
        LOCATION;LANGUAGE=en:Copenhagen

   Figure 215

8.7.3.  Group or List Membership

   Parameter this property:

         DTSTART:19980118T073000Z

3.8.2.5.  Duration

   Property Name: MEMBER DURATION

   Purpose: To specify the group or list membership The property specifies a positive duration of the calendar user
   specified by the property.

   Description: This parameter time.

   Value Type: DURATION

   Property Parameters: Non-standard property parameters can be
      specified on properties with a
   CAL-ADDRESS value type. this property.

   Conformance: The parameter identifies the groups property can be specified in "VEVENT", "VTODO",
      "VFREEBUSY" or list
   membership for the "VALARM" calendar user specified by the property.  The
   parameter value either components.

   Description: In a single "VEVENT" calendar address in a quoted-string
   or component the property may be
      used to specify a COMMA character (US-ASCII decimal 44) list duration of calendar
   addresses, each in the event, instead of an explicit
      end date/time.  In a quoted-string.  The individual "VTODO" calendar address
   parameter values MUST each component the property may
      be specified in used to specify a quoted-string.

   Format Definition: The property parameter is defined by duration for the following
   notation:

        memberparam        = "MEMBER" "=" DQUOTE cal-address DQUOTE
                             *("," DQUOTE cal-address DQUOTE)

   Example:

        ATTENDEE;MEMBER="MAILTO:ietf-calsch@imc.org":
        MAILTO:jsmith@host.com

        ATTENDEE;MEMBER="MAILTO:projectA@host.com",
        "MAILTO:projectB@host.com":
        MAILTO:janedoe@host.com

   Figure 217

8.7.4.  Alternate Text Representation

   Parameter Name: ALTREP

   Purpose: To specify to-do, instead of an alternate text representation for
      explicit due date/time.  In a "VFREEBUSY" calendar component the
      property
   value. may be used to specify the interval of free time being
      requested.  In a "VALARM" calendar component the property may be
      used to specify the delay period prior to repeating an alarm.

   Format Definition: The property parameter is defined by the following notation:

        altrepparam

         duration   = "ALTREP" "=" DQUOTE uri DQUOTE

   Description: The parameter specifies "DURATION" durparam ":" dur-value CRLF
                      ;consisting of a URI that points to positive duration of time.

         durparam   = *(";" xparam)

   Example: The following is an
   alternate representation for a textual property value.  A property
   specifying example of this parameter MUST also include a value property that reflects the
   default representation specifies
      an interval of the text value. time of 1 hour and zero minutes and zero seconds:

         DURATION:PT1H0M0S

      The individual URI
   parameter values MUST each be specified in a quoted-string.

   Example:

        DESCRIPTION;ALTREP="CID:<part3.msg.970415T083000@host.com>"
        :Project XYZ Review Meeting will include the following agenda
         items: (a) Market Overview, (b) Finances, (c) Project
         Management

   The "ALTREP" is an example of this property parameter value might point to a "text/html"
   content portion.

        Content-Type:text/html
        Content-Id:<part3.msg.970415T083000@host.com>

        <html><body>
        <p><b>Project XYZ Review Meeting</b> will include the following
        agenda items:<ol><li>Market
        Overview</li><li>Finances</li><li>Project Management</li>
        </ol></p></body></html>

8.7.5.  Inline Encoding

   Parameter that specifies an
      interval of time of 15 minutes.

         DURATION:PT15M

3.8.2.6.  Free/Busy Time

   Property Name: ENCODING FREEBUSY

   Purpose: To specify an alternate inline encoding for the property
   value.

   Description: The property parameter identifies the inline encoding
   used in a property value. The default encoding is "8BIT",
   corresponding to a property value consisting of text. defines one or more free or busy time
      intervals.

   Value Type: PERIOD.  The "BASE64"
   encoding type corresponds to a property value encoded using the
   "BASE64" encoding defined date and time values MUST be in [RFC 2045].

   If the value an UTC time
      format.

   Property Parameters: Non-standard or free/busy time type parameter is ";VALUE=BINARY", then the inline
   encoding parameter MUST property
      parameters can be specified with the value
   ";ENCODING=BASE64".

   Format Definition: on this property.

   Conformance: The property parameter is defined by the following
   notation:

        encodingparam      = "ENCODING" "="
                             ("8BIT"
           ; "8bit" text encoding is defined in [RFC 2045]
                           / "BASE64"
           ; "BASE64" binary encoding format is defined can be specified in [RFC 2045]
                           / iana-token
           ; Some other IANA registered iCalendar encoding type
                           / x-name)
           ; A non-standard, experimental encoding type

   Example:

        ATTACH;FMTYPE=IMAGE/JPEG;ENCODING=BASE64;VALUE=BINARY:MIICajC
         CAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQAwdzELMAkGA1UEBhMCVVMxLDA
         qBgNVBAoTI05ldHNjYXBlIENvbW11bmljYXRpb25zIENvcnBvcmF0aW9uMRw
         <...remainder of "BASE64" encoded binary data...>

   Figure 222

8.7.6.  Format Type

   Parameter Name: FMTTYPE

   Purpose: To specify the content type of a referenced object. "VFREEBUSY" calendar
      component.

   Description: This parameter These time periods can be specified on properties that are
   used to reference an object. as either a start
      and end date-time or a start date-time and duration.  The parameter specifies the content
   type of date and
      time MUST be a UTC time format.

      "FREEBUSY" properties within the referenced object.  For example, "VFREEBUSY" calendar component
      SHOULD be sorted in ascending order, based on start time and then
      end time, with the "ATTACH"
   property, a FTP type URI value does not, earliest periods first.

      The "FREEBUSY" property can specify more than one value, separated
      by itself, necessarily
   convey the type of content associated with COMMA character (US-ASCII decimal 44).  In such cases, the resource.  The
   parameter value MUST
      "FREEBUSY" property values SHOULD all be of the TEXT for either an IANA registered
   content same "FBTYPE"
      property parameter type or (e.g., all values of a non-standard content type. particular "FBTYPE"
      listed together in a single property).

   Format Definition: The property parameter is defined by the following notation:

        fmttypeparam

         freebusy   = "FMTTYPE" "=" iana-token "FREEBUSY" fbparam ":" fbvalue
                      CRLF

         fbparam    = *(
                    ; A IANA registered content type the following is optional,
                    ; but MUST NOT occur more than once

                    (";" fbtypeparam) / x-name

                    ; A non-standard content type the following is optional,
                    ; and MAY occur more than once

                    (";" xparam)

                    )

         fbvalue    = period *["," period]
         ;Time value MUST be in the UTC time format.

   Example:

         ATTACH;FMTTYPE=application/binary:ftp://domain.com/pub/docs/
          agenda.doc

   Figure 224

8.7.7.  Non-standard Properties The following are some examples of this property:

     FREEBUSY;FBTYPE=BUSY-UNAVAILABLE:19970308T160000Z/PT8H30M

     FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H

     FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H,
      19970308T230000Z/19970309T000000Z

3.8.2.7.  Time Transparency
   Property Name: Any property name with a "X-" prefix TRANSP

   Purpose: This class of property provides a framework for defining
   non-standard properties. defines whether an event is transparent or not
      to busy time searches.

   Value Type: TEXT

   Property Parameters: Non-standard and language property parameters can be
      specified on this property.

   Conformance: This property can be specified once in any a "VEVENT"
      calendar component.

   Description: The MIME Calendaring and Scheduling Content Type
   provides a "standard mechanism for doing non-standard things".  This
   extension support Time Transparency is provided for implementers to "push the envelope"
   on the existing version of the memo.  Extension properties are
   specified by property and/or property parameter names that have the
   prefix text characteristic of "X-" (the two character sequence: LATIN CAPITAL LETTER
   X character followed by the HYPEN-MINUS character).  It is
   recommended an event that vendors concatenate onto this sentinel another short
   prefix text
      determines whether it appears to identify consume time on a calendar.
      Events that consume actual time for the vendor.  This will facilitate readability
   of individual or resource
      associated with the extensions and minimize possible collision of names between
   different vendors.  User agents that support this content type are
   expected to calendar SHOULD be able recorded as OPAQUE,
      allowing them to parse the extension properties and property
   parameters but can ignore them.

   At present, there is no registration authority for names of extension
   properties and property parameters.  The data type for this property
   is TEXT.  Optionally, the data type can be any of detected by free-busy time searches.  Other
      events, which do not take up the other valid
   data types. individual's (or resource's) time
      SHOULD be recorded as TRANSPARENT, making them invisible to free-
      busy time searches.

   Format Definition: The property is defined by the following notation:

        x-prop

     transp     = x-name *(";" xparam)
        [";" languageparam] "TRANSP" tranparam ":" text transvalue CRLF
           ; Lines longer than 75 octets should be folded

     tranparam  = *(";" xparam)

     transvalue = "OPAQUE"      ;Blocks or opaque on busy time searches.
                / "TRANSPARENT" ;Transparent on busy time searches.
        ;Default value is OPAQUE

   Example: The following might be the ABC vendor's extension is an example of this property for an
   audio-clip form event
      that is transparent or does not block on free/busy time searches:

         TRANSP:TRANSPARENT

      The following is an example of subject property:

                      X-ABC-MMSUBJ;X-ABC-MMSUBJTYPE=wave:
                      http://load.noise.org/mysubj.wav

   Figure 226

8.7.8.  Request Status this property for an event that is
      opaque or blocks on free/busy time searches:

         TRANSP:OPAQUE

3.8.3.  Time Zone Component Properties

   The following properties specify time zone information in calendar
   components.

3.8.3.1.  Time Zone Identifier

   Property Name: REQUEST-STATUS TZID

   Purpose: This property defines specifies the status code returned for a
   scheduling request. text value that uniquely
      identifies the "VTIMEZONE" calendar component.

   Value Type: TEXT

   Property Parameters: Non-standard and language property parameters can be
      specified on this property.

   Conformance: The This property can MUST be specified in "VEVENT", "VTODO",
   "VJOURNAL" or "VFREEBUSY" a "VTIMEZONE"
      calendar component.

   Description: This property is used to return status code information
   related to the processing of an associated label by which a time zone calendar
      component is referenced by any iCalendar object.  The properties whose data
      type for this property is TEXT.

   The value consists of a short return status component, a longer
   return status description component, either DATE-TIME or TIME and optionally not intended to specify a status-specific
   data component. UTC
      or a "floating" time.  The components presence of the value are separated by the
   SEMICOLON SOLIDUS character (US-ASCII (US-
      ASCII decimal 59).

   The short return status is 47) as a PERIOD character (US-ASCII decimal 46)
   separated 3-tuple of integers.  For example, "3.1.1".  The successive
   levels of integers provide for prefix, indicates that this TZID represents
      an unique ID in a successive level of status code
   granularity.

   The following are initial classes for the return status code.

   Individual iCalendar object methods will globally defined time zone registry (when such
      registry is defined).

         Note: This document does not define specific return
   status codes a naming convention for these classes.  In addition, other classes for the
   return status code
         time zone identifiers.  Implementers may be defined using want to use the registration process naming
         conventions defined later in existing time zone specifications such
         as the public-domain Olson database [TZDB].  The specification
         of globally unique time zone identifiers is not addressed by
         this memo.

                Request Status Return Codes document and Description

   +-----------------+-------------------------------------------------+
   | Short Return    | Longer Return Status Description                |
   | Status Code     |                                                 |
   +-----------------+-------------------------------------------------+
   | 1.xx            | Preliminary success.  This class of status code |
   |                 | indicates that the request has been initially   |
   |                 | processed but that completion is pending.       |
   |                 |                                                 |
   | 2.xx            | Successful.  This class of status code          |
   |                 | indicates that the request was completed        |
   |                 | successfuly.  However, left for future study.

   Format Definition: The property is defined by the exact status code    |
   |                 | can indicate that a fallback has been taken.    |
   |                 |                                                 |
   | 3.xx            | Client Error.  This class following notation:

         tzid       = "TZID" tzidpropparam ":" [tzidprefix] text CRLF

         tzidpropparam      = *(";" xparam)

         ;tzidprefix        = "/"
         ; Defined previously. Just listed here for reader convenience.

   Example: The following are examples of status code        |
   |                 | indicates that the request was not successful.  |
   |                 | non-globally unique time zone
      identifiers:

         TZID:US-Eastern

         TZID:California-Los_Angeles
      The error following is the result an example of either a syntax or a |
   |                 | semantic error in fictitious globally unique time
      zone identifier:

         TZID:/US-New_York-New_York

3.8.3.2.  Time Zone Name

   Property Name: TZNAME

   Purpose: This property specifies the client formatted request. |
   |                 | Request should not customary designation for a time
      zone description.

   Value Type: TEXT

   Property Parameters: Non-standard and language property parameters
      can be retried until the         |
   |                 | condition specified on this property.

   Conformance: This property can be specified in the request is corrected.          |
   |                 |                                                 |
   | 4.xx            | Scheduling Error. a "VTIMEZONE" calendar
      component.

   Description: This class of status code    |
   |                 | indicates that the request was not successful.  |
   |                 | Some sort of error occurred within the          |
   |                 | calendaring and scheduling service, not         |
   |                 | directly related property may be specified in multiple languages; in
      order to the request itself.         |
   +-----------------+-------------------------------------------------+ provide for different language requirements.

   Format Definition: The property is defined by the following notation:

        rstatus

         tzname     = "REQUEST-STATUS" rstatparam "TZNAME" tznparam ":"
                     statcode ";" statdesc [";" extdata]

        rstatparam text CRLF

         tznparam   = *(

                    ; the following is optional,
                    ; but MUST NOT occur more than once

                    (";" languageparm) languageparam) /

                    ; the following is optional,
                    ; and MAY occur more than once

                    (";" xparam)

                    )

        statcode   = 1*DIGIT *("." 1*DIGIT)
        ;Hierarchical, numeric return status code

        statdesc   = text
        ;Textual status description

        extdata    = text
        ;Textual exception data. For example, the offending property
        ;name and value or complete property line.

   Example: The following are some possible examples example of this property. property:

         TZNAME:EST
      The COMMA and SEMICOLON separator characters in the following is an example of this property value when two different
      languages for the time zone name are BACKSLASH character escaped because they appear specified:

         TZNAME;LANGUAGE=en:EST
         TZNAME;LANGUAGE=fr-CA:HNE

3.8.3.3.  Time Zone Offset From

   Property Name: TZOFFSETFROM

   Purpose: This property specifies the offset which is in a text value.

        REQUEST-STATUS:2.0;Success

        REQUEST-STATUS:3.1;Invalid use prior to
      this time zone observance.

   Value Type: UTC-OFFSET

   Property Parameters: Non-standard property value;DTSTART:96-Apr-01

        REQUEST-STATUS:2.8; Success\, repeating event ignored. Scheduled
         as parameters can be
      specified on this property.

   Conformance: This property MUST be specified in a single event.;RRULE:FREQ=WEEKLY\;INTERVAL=2

        REQUEST-STATUS:4.1;Event conflict. Date/time is busy.

        REQUEST-STATUS:3.7;Invalid "VTIMEZONE"
      calendar user;ATTENDEE:
         MAILTO:jsmith@host.com

   Figure 228

9.  iCalendar Object Examples

   The following examples are provided as an informational source of
   illustrative iCalendar objects consistent with this content type.

   The following example specifies a three-day conference that begins at
   8:00 AM EDT, September 18, 1996 and end at 6:00 PM EDT, September 20,
   1996.

        BEGIN:VCALENDAR PRODID:-//xyz Corp//NONSGML PDA Calendar Verson
        1.0//EN VERSION:2.0 BEGIN:VEVENT DTSTAMP:19960704T120000Z
        UID:uid1@host.com ORGANIZER:MAILTO:jsmith@host.com
        DTSTART:19960918T143000Z DTEND:19960920T220000Z STATUS:CONFIRMED

        CATEGORIES:CONFERENCE SUMMARY:Networld+Interop Conference
        DESCRIPTION:Networld+Interop Conference
          and Exhibit\nAtlanta World Congress Center\n
         Atlanta, Georgia END:VEVENT END:VCALENDAR

   The following example component.

   Description: This property specifies a group scheduled meeting that begin
   at 8:30 AM EST on March 12, 1998 and end the offset which is in use prior
      to this time observance.  It is used to calculate the absolute
      time at 9:30 AM EST on March 12,
   1998.  The "Organizer" has scheduled which the meeting with one or more
   calendar users transition to a given observance takes place.
      This property MUST only be specified in a group. "VTIMEZONE" calendar
      component.  A time zone specification for Eastern
   United States has been specified.

        BEGIN:VCALENDAR
        PRODID:-//RDU Software//NONSGML HandCal//EN
        VERSION:2.0
        BEGIN:VTIMEZONE
        TZID:US-Eastern
        BEGIN:STANDARD
        DTSTART:19981025T020000
        RDATE:19981025T020000
        TZOFFSETFROM:-0400
        TZOFFSETTO:-0500
        TZNAME:EST
        END:STANDARD
        BEGIN:DAYLIGHT
        DTSTART:19990404T020000
        RDATE:19990404T020000
        TZOFFSETFROM:-0500
        TZOFFSETTO:-0400
        TZNAME:EDT
        END:DAYLIGHT
        END:VTIMEZONE
        BEGIN:VEVENT
        DTSTAMP:19980309T231000Z
        UID:guid-1.host1.com
        ORGANIZER;ROLE=CHAIR:MAILTO:mrbig@host.com
        ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT;CUTYPE=GROUP:
         MAILTO:employee-A@host.com
        DESCRIPTION:Project XYZ Review Meeting
        CATEGORIES:MEETING
        CLASS:PUBLIC
        CREATED:19980309T130000Z
        SUMMARY:XYZ Project Review
        DTSTART;TZID=US-Eastern:19980312T083000
        DTEND;TZID=US-Eastern:19980312T093000
        LOCATION:1CP Conference Room 4350
        END:VEVENT
        END:VCALENDAR "VTIMEZONE" calendar component MUST include this
      property.  The following property value is an example of an iCalendar object passed in a MIME
   message with a single body part consisting signed numeric indicating the
      number of a "text/calendar"
   Content Type.

        TO:jsmith@host1.com
        FROM:jdoe@host1.com
        MIME-VERSION:1.0
          MESSAGE-ID<id3@host1.com>
        CONTENT-TYPE:text/calendar

        BEGIN:VCALENDAR
        METHOD:xyz
        VERSION:2.0
        PRODID:-//ABC Corporation//NONSGML My Product//EN
        BEGIN:VEVENT
        DTSTAMP:19970324T1200Z
        SEQUENCE:0
        UID:uid3@host1.com
        ORGANIZER:MAILTO:jdoe@host1.com
        ATTENDEE;RSVP=TRUE:MAILTO:jsmith@host1.com
        DTSTART:19970324T123000Z
        DTEND:19970324T210000Z
        CATEGORIES:MEETING,PROJECT
        CLASS:PUBLIC
        SUMMARY:Calendaring Interoperability Planning Meeting
        DESCRIPTION:Discuss how we can test interoperability\n
         using iCalendar hours and other IETF standards.
        LOCATION:LDB Lobby
        ATTACH;FMTTYPE=application/postscript:ftp://xyzCorp.com/pub/
         conf/bkgrnd.ps
        END:VEVENT
        END:VCALENDAR possibly minutes from UTC.  Positive numbers
      represent time zones east of the prime meridian, or ahead of UTC.
      Negative numbers represent time zones west of the prime meridian,
      or behind UTC.

   Format Definition: The following property is an example defined by the following notation:

         tzoffsetfrom       = "TZOFFSETFROM" frmparam ":" utc-offset
                              CRLF

         frmparam   = *(";" xparam)

   Example: The following are examples of a to-do due this property:

         TZOFFSETFROM:-0500

         TZOFFSETFROM:+1345

3.8.3.4.  Time Zone Offset To

   Property Name: TZOFFSETTO

   Purpose: This property specifies the offset which is in use in this
      time zone observance.

   Value Type: UTC-OFFSET

   Property Parameters: Non-standard property parameters can be
      specified on April 15, 1998.  An
   audio alarm has been this property.

   Conformance: This property MUST be specified to remind the in a "VTIMEZONE"
      calendar user at noon,
   the day before component.

   Description: This property specifies the to-do offset which is expected in use in
      this time zone observance.  It is used to be completed and repeat
   hourly, four additional times.  The to-do definition has been
   modified twice since it was initially created.

        BEGIN:VCALENDAR
        VERSION:2.0
        PRODID:-//ABC Corporation//NONSGML My Product//EN
        BEGIN:VTODO
        DTSTAMP:19980130T134500Z
        SEQUENCE:2
        UID:uid4@host1.com
        ORGANIZER:MAILTO:unclesam@us.gov
        ATTENDEE;PARTSTAT=ACCEPTED:MAILTO:jqpublic@host.com
        DUE:19980415T235959
        STATUS:NEEDS-ACTION
        SUMMARY:Submit Income Taxes
        BEGIN:VALARM
        ACTION:AUDIO
        TRIGGER:19980403T120000
        ATTACH;FMTTYPE=audio/basic:http://host.com/pub/audio-
         files/ssbanner.aud
        REPEAT:4
        DURATION:PT1H
        END:VALARM
        END:VTODO
        END:VCALENDAR calculate the absolute
      time for the new observance.  The following property value is an example of a journal entry.

        BEGIN:VCALENDAR
        VERSION:2.0
        PRODID:-//ABC Corporation//NONSGML My Product//EN
        BEGIN:VJOURNAL
        DTSTAMP:19970324T120000Z
        UID:uid5@host1.com
        ORGANIZER:MAILTO:jsmith@host.com
        STATUS:DRAFT
        CLASS:PUBLIC
        CATEGORY:Project Report, XYZ, Weekly Meeting
        DESCRIPTION:Project xyz Review Meeting Minutes\n
         Agenda\n1. Review signed
      numeric indicating the number of project version 1.0 requirements.\n2.
        Definition hours and possibly minutes from
      UTC.  Positive numbers represent time zones east of project processes.\n3. Review the prime
      meridian, or ahead of UTC.  Negative numbers represent time zones
      west of project schedule.\n
         Participants: John Smith, Jane Doe, Jim Dandy\n-It was
          decided that the requirements need prime meridian, or behind UTC.

   Format Definition: The property is defined by the following notation:

         tzoffsetto = "TZOFFSETTO" toparam ":" utc-offset CRLF

         toparam    = *(";" xparam)

   Example: The following are examples of this property:

         TZOFFSETTO:-0400

         TZOFFSETTO:+1245

3.8.3.5.  Time Zone URL

   Property Name: TZURL

   Purpose: The TZURL provides a means for a VTIMEZONE component to
      point to a network location that can be signed off by
          product marketing.\n-Project processes were accepted.\n
         -Project schedule needs used to account for scheduled holidays
          and employee vacation time. Check with HR retrieve an up-to-
      date version of itself.

   Value Type: URI
   Property Parameters: Non-standard property parameters can be
      specified on this property.

   Conformance: This property can be specified in a "VTIMEZONE" calendar
      component.

   Description: The TZURL provides a means for specific
          dates.\n-New schedule will a VTIMEZONE component to
      point to a network location that can be distributed by Friday.\n-
         Next weeks meeting used to retrieve an up-to-
      date version of itself.  This provides a hook to handle changes
      government bodies impose upon time zone definitions.  Retrieval of
      this resource results in an iCalendar object containing a single
      VTIMEZONE component and a METHOD property set to PUBLISH.

   Format Definition: The property is cancelled. No meeting until 3/23.
        END:VJOURNAL
        END:VCALENDAR defined by the following notation:

         tzurl      = "TZURL" tzurlparam ":" uri CRLF

         tzurlparam = *(";" xparam)

   Example: The following is an example of published busy time information. this property:

         TZURL:http://timezones.r.us.net/tz/US-California-Los_Angeles

3.8.4.  Relationship Component Properties

   The following properties specify relationship information in calendar
   components.

3.8.4.1.  Attendee

   Property Name: ATTENDEE

   Purpose: The property defines an "Attendee" within a calendar
      component.

   Value Type: CAL-ADDRESS

   Property Parameters: Non-standard, language, calendar user type,
      group or list membership, participation role, participation
      status, RSVP expectation, delegatee, delegator, sent by, common
      name or directory entry reference property parameters can be
      specified on this property.

   Conformance: This property MUST be specified in an iCalendar object might
      that specifies a group scheduled calendar entity.  This property
      MUST NOT be placed specified in an iCalendar object when publishing the network resource
   www.host.com/calendar/busytime/jsmith.ifb.

        BEGIN:VCALENDAR
        VERSION:2.0
        PRODID:-//RDU Software//NONSGML HandCal//EN
        BEGIN:VFREEBUSY
        ORGANIZER:MAILTO:jsmith@host.com
        DTSTART:19980313T141711Z
        DTEND:19980410T141711Z
        FREEBUSY:19980314T233000Z/19980315T003000Z
        FREEBUSY:19980316T153000Z/19980316T163000Z
        FREEBUSY:19980318T030000Z/19980318T040000Z
        URL:http://www.host.com/calendar/busytime/jsmith.ifb
        END:VFREEBUSY
        END:VCALENDAR

10.  Recommended Practices

   These recommended practices should be followed
      calendar information (e.g., NOT in order to assure
   consistent handling of the following cases for an iCalendar object.

   1.  Content lines longer than 75 octets SHOULD be folded.

   2.  A calendar entry with object that
      specifies the publication of a "DTSTART" property but no "DTEND" calendar user's busy time, event,
      to-do or journal).  This property does not take up any time.  It is intended to represent not specified in an
   event iCalendar
      object that is associated with specifies only a given calendar date and time of day,
   such as an anniversary.  Since the event does zone definition or that defines
      calendar entities that are not take up any time,
   it group scheduled entities, but are
      entities only on a single user's calendar.

   Description: The property MUST NOT only be used specified within calendar
      components to record busy time no matter what specify participants, non-participants and the value for chair
      of a group scheduled calendar entity.  The property is specified
      within an "EMAIL" category of the "TRANSP" property.

   3.  When "VALARM" calendar component to
      specify an email address that is to receive the "DTSTART" and "DTEND", email type of
      iCalendar alarm.

      The property parameter CN is for "VEVENT", "VJOURNAL" and
   "VFREEBUSY" the common or displayable name
      associated with the calendar components, and "DTSTART" and "DUE", address; ROLE, for "VTODO"
   calendar components, have the same value data type (e.g., DATE-TIME),
   they SHOULD specify values intended role
      that the attendee will have in the same time format (e.g., UTC time
   format).

   4.  When calendar component; PARTSTAT,
      for the combination status of the "RRULE" and "RDATE" properties on an
   iCalendar object produces multiple instances having the same start
   date/time, they should be collapsed to, and considered as, a single
   instance.

   5.  When a calendar user receives multiple requests attendee's participation; RSVP, for
      indicating whether the same
   calendar component (e.g., REQUEST for a "VEVENT" calendar component)
   as favor of a result reply is requested; CUTYPE, to
      indicate the type of being on multiple mailing lists specified by
   "ATTENDEE" properties in calendar user; MEMBER, to indicate the request, they SHOULD respond groups
      that the attendee belongs to; DELEGATED-TO, to only one
   of indicate the requests.  The
      calendar user SHOULD also specify (using users that the
   "MEMBER" parameter of original request was delegated to; and
      DELEGATED-FROM, to indicate whom the "ATTENDEE" property) which mailing list
   they are a member of.

   6.  An implementation can truncate a "SUMMARY" property value request was delegated from;
      SENT-BY, to 255
   characters.

   7.  If seconds indicate whom is acting on behalf of the minute are not supported by ATTENDEE; and
      DIR, to indicate the URI that points to the directory information
      corresponding to the attendee.  These property parameters can be
      specified on an implementation,
   then "ATTENDEE" property in either a value of "00" SHOULD "VEVENT", "VTODO"
      or "VJOURNAL" calendar component.  They MUST not be specified for the seconds component in
      an "ATTENDEE" property in a time value.

   8. "VFREEBUSY" or "VALARM" calendar
      component.  If the value type LANGUAGE property parameter (VALUE=) contains an unknown value
   type, it SHOULD be treated as TEXT.

   9.  TZURL values SHOULD NOT be specified as a FILE URI type.  This
   URI form can be useful within an organization, but is problematic in specified, the Internet.

   10.  Some possible English
      identified language applies to the CN parameter.

      A recipient delegated a request MUST inherit the RSVP and ROLE
      values for CATEGORIES property include
   "ANNIVERSARY", "APPOINTMENT", "BUSINESS", "EDUCATION", "HOLIDAY",
   "MEETING", "MISCELLANEOUS", "NON-WORKING HOURS", "NOT IN OFFICE",
   "PERSONAL", "PHONE CALL", "SICK DAY", "SPECIAL OCCASION", "TRAVEL",
   "VACATION".  Categories from the attendee that delegated the request to them.

      Multiple attendees can be specified in any registered language.

   11.  Some possible English values for RESOURCES by including multiple
      "ATTENDEE" properties within the calendar component.

   Format Definition: The property include
   "CATERING", "CHAIRS", "COMPUTER PROJECTOR", "EASEL", "OVERHEAD
   PROJECTOR", "SPEAKER PHONE", "TABLE", "TV", "VCR", "VIDEO PHONE",
   "VEHICLE".  Resources can be specified in any registered language.

11.  Registration of Content Type Elements

   This section provides is defined by the process for registration of MIME
   Calendaring and Scheduling Content Type iCalendar object methods and
   new or modified properties.

11.1.  Registration of New and Modified iCalendar Object Methods

   New MIME Calendaring and Scheduling Content Type iCalendar object
   methods are registered by following notation:

         attendee   = "ATTENDEE" attparam ":" cal-address CRLF

         attparam   = *(

                    ; the publication of an IETF Request for
   Comments (RFC).  Changes to an iCalendar object method following are registered
   by optional,
                    ; but MUST NOT occur more than once

                    (";" cutypeparam) / (";"memberparam) /
                    (";" roleparam) / (";" partstatparam) /
                    (";" rsvpparam) / (";" deltoparam) /
                    (";" delfromparam) / (";" sentbyparam) /
                    (";"cnparam) / (";" dirparam) /
                    (";" languageparam) /

                    ; the publication following is optional,
                    ; and MAY occur more than once

                    (";" xparam)

                    )

   Example: The following are examples of this property's use for a revision of the RFC defining the method.

11.2.  Registration
      to-do:

     ORGANIZER:MAILTO:jsmith@host1.com
     ATTENDEE;MEMBER="MAILTO:DEV-GROUP@host2.com":
      MAILTO:joecool@host2.com
     ATTENDEE;DELEGATED-FROM="MAILTO:immud@host3.com":
      MAILTO:ildoit@host1.com

      The following is an example of New Properties

   This section defines procedures by which new properties or enumerated this property values for the MIME Calendaring and Scheduling Content Type
   can be registered with the IANA.  Non-IANA properties can be used by
   bilateral agreement, provided the associated properties names follow
   the "X-" convention.

   The procedures defined here are designed for specifying
      multiple attendees to allow public comment and
   review an event:

     ORGANIZER:MAILTO:jsmith@host1.com
     ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;CN=Henry Cabot
      :MAILTO:hcabot@host2.com
     ATTENDEE;ROLE=REQ-PARTICIPANT;DELEGATED-FROM="MAILTO:bob@host.com"
      ;PARTSTAT=ACCEPTED;CN=Jane Doe:MAILTO:jdoe@host1.com

      The following is an example of new properties, while posing only this property with a small impediment URI to the
   definition of new properties.

   Registration of a new property is accomplished by
      directory information associated with the attendee:

     ATTENDEE;CN=John Smith;DIR="ldap://host.com:6666/o=eDABC%
      20Industries,c=3DUS??(cn=3DBJim%20Dolittle)":MAILTO:jimdo@
      host1.com
      The following
   steps.

11.3.  Define the property

   A property is defined by completing the following template.

        To: ietf-calendar@imc.org

        Subject: Registration an example of text/calendar MIME this property XXX

        Property name:

        Property purpose:

        Property value type(s):

        Property parameter (s):

        Conformance:

        Description:

        Format definition:

        Examples: with "delegatee" and
      "delegator" information for an event:

     ORGANIZER;CN=John Smith:MAILTO:jsmith@host.com
     ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;DELEGATED-FROM=
      "MAILTO:iamboss@host2.com";CN=Henry Cabot:MAILTO:hcabot@
      host2.com
     ATTENDEE;ROLE=NON-PARTICIPANT;PARTSTAT=DELEGATED;DELEGATED-TO=
      "MAILTO:hcabot@host2.com";CN=The Big Cheese:MAILTO:iamboss
      @host2.com
     ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=ACCEPTED;CN=Jane Doe
      :MAILTO:jdoe@host1.com

   Example: The meaning of each field in the template following is as follows.

   Property name: The name of the property, as it will appear in the
   body of an text/calendar MIME Content-Type "property: value" line to
   the left example of this property's use when
      another calendar user is acting on behalf of the colon ":". "Attendee":

     ATTENDEE;SENT-BY=MAILTO:jan_doe@host1.com;CN=John Smith:MAILTO:
      jsmith@host1.com

3.8.4.2.  Contact

   Property purpose: Name: CONTACT

   Purpose: The purpose of the property (e.g., is used to indicate a
   delegate for the event represent contact information or to-do, etc.).  Give a short but clear
   description.

   Property value type (s): Any of the valid value types for the
   property value needs to be specified.  The default value type also
   needs to be specified.  If
      alternately a new value type is specified, it needs reference to
   be declared in this section.

   Property parameter (s): Any of contact information associated with the valid
      calendar component.

   Value Type: TEXT

   Property Parameters: Non-standard, alternate text representation and
      language property parameters for the
   property needs to can be specified. specified on this property.

   Conformance: The calendar components that the property can appear in
   needs to be specified. specified in a "VEVENT", "VTODO",
      "VJOURNAL" or "VFREEBUSY" calendar component.

   Description: Any special notes about the property, how it is to be
   used, etc.

   Format definition: The ABNF for the property definition needs to be
   specified.

   Examples: One or more examples of instances value consists of textual contact
      information.  An alternative representation for the property needs to value
      can also be specified.

11.4.  Post the Property definition

   The property description MUST be posted specified that refers to the new property
   discussion list, ietf-calendar@imc.org.

11.5.  Allow a comment period

   Discussion on the new property MUST be allowed URI pointing to take place on the
   list for an
      alternate form, such as a minimum of two weeks.  Consensus MUST be reached on vCard [RFC2426], for the contact
      information.

   Format Definition: The property before proceeding to is defined by the next step.

11.6.  Submit following notation:

         contact    = "CONTACT" contparam ":" text CRLF

         contparam  = *(
                    ; the property for approval

   Once following are optional,
                    ; but MUST NOT occur more than once

                    (";" altrepparam) / (";" languageparam) /

                    ; the two-week comment period has elapsed, following is optional,
                    ; and the proposer MAY occur more than once

                    (";" xparam)

                    )

   Example: The following is
   convinced consensus has been reached on the property, the
   registration application should be submitted to the Method Reviewer
   for approval. an example of this property referencing
      textual contact information:

     CONTACT:Jim Dolittle\, ABC Industries\, +1-919-555-1234

      The Method Reviewer following is appointed an example of this property with an alternate
      representation of a LDAP URI to a directory entry containing the Application
   Area Directors and can either accept or reject the
      contact information:

     CONTACT;ALTREP="ldap://host.com:6666/o=3DABC%20Industries\,
      c=3DUS??(cn=3DBJim%20Dolittle)":Jim Dolittle\, ABC Industries\,
      +1-919-555-1234

      The following is an example of this property
   registration.  An accepted registration should be passed on by the
   Method Reviewer to with an alternate
      representation of a MIME body part containing the IANA for inclusion contact
      information, such as a vCard [RFC2426] embedded in a [MIME-DIR]
      content-type:

     CONTACT;ALTREP="CID=<part3.msg970930T083000SILVER@host.com>":Jim
       Dolittle\, ABC Industries\, +1-919-555-1234

      The following is an example of this property referencing a network
      resource, such as a vCard [RFC2426] object containing the official IANA method
   registry. contact
      information:

     CONTACT;ALTREP="http://host.com/pdi/jdoe.vcf":Jim
       Dolittle\, ABC Industries\, +1-919-555-1234

3.8.4.3.  Organizer
   Property Name: ORGANIZER

   Purpose: The registration property defines the organizer for a calendar component.

   Value Type: CAL-ADDRESS

   Property Parameters: Non-standard, language, common name, directory
      entry reference, sent by property parameters can be rejected for any of the following
   reasons. 1) Insufficient comment period; 2) Consensus not reached; 3)
   Technical deficiencies raised specified on
      this property.

   Conformance: This property MUST be specified in an iCalendar object
      that specifies a group scheduled calendar entity.  This property
      MUST be specified in an iCalendar object that specifies the list
      publication of a calendar user's busy time.  This property MUST
      NOT be specified in an iCalendar object that specifies only a time
      zone definition or elsewhere have that defines calendar entities that are not been
   addressed.
      group scheduled entities, but are entities only on a single user's
      calendar.

   Description: The Method Reviewer's decision property is specified within the "VEVENT", "VTODO",
      "VJOURNAL calendar components to reject specify the organizer of a group
      scheduled calendar entity.  The property can
   be appealed by is specified within the proposer
      "VFREEBUSY" calendar component to specify the IESG, or the objections raised can
   be addressed by calendar user
      requesting the proposer and free or busy time.  When publishing a "VFREEBUSY"
      calendar component, the property resubmitted.

11.7.  Property Change Control

   Existing properties can be changed using the same process by which
   they were registered.

   1.  Define is used to specify the change

   2.  Post calendar
      that the change

   3.  Allow a comment period

   4.  Submit published busy time came from.

      The property has the property parameters CN, for approval

   Note that specifying the original author
      common or any other interested party can
   propose display name associated with the "Organizer", DIR, for
      specifying a change pointer to an existing property, but the directory information associated with
      the "Organizer", SENT-BY, for specifying another calendar user
      that such changes
   should only be proposed when there are serious omissions or errors in is acting on behalf of the published memo. "Organizer".  The Method Reviewer can object to a change if it
   is not backward compatible, but is not required to do so.

   Property definitions can never non-standard
      parameters may also be deleted from specified on this property.  If the IANA registry, but
   properties which are no longer believed to be useful can be declared
   OBSOLETE by a change
      LANGUAGE property parameter is specified, the identified language
      applies to their "intended use" field.

12.  Property Parameters the CN parameter value.

   Format Definition: The general property parameters defined by this memo are is defined by the following notation:

     parameter

         organizer  = altrepparam           ; Alternate text representation
               / cnparam               ; Common name
               / cutypeparam           ; Calendar user type
               / delfromparam          ; Delegator
               / deltoparam            ; Delegatee
               / dirparam              ; Directory entry
               / encodingparam         ; Inline encoding
               / fmttypeparam          ; Format type
               / fbtypeparam           ; Free/busy time type
               / languageparam         ; Language for text
               / memberparam           ; Group or list membership
               / partstatparam         ; Participation status
               / rangeparam            ; Recurrence identifier range
               / trigrelparam          ; Alarm trigger relationship
               / reltypeparam          ; Relationship type
               / roleparam "ORGANIZER" orgparam ":"
                      cal-address CRLF

         orgparam   = *(

                    ; Participation role
               / rsvpparam the following are optional,
                    ; RSVP expectation but MUST NOT occur more than once

                    (";" cnparam) / sentbyparam           ; Sent by (";" dirparam) / tzidparam             ; Reference to time zone object (";" sentbyparam) / valuetypeparam        ; Property value data type
                    (";" languageparam) / ianaparam

                    ; Some other IANA registered iCalendar parameter.
               / xparam the following is optional,
                    ; A non-standard, experimental parameter.

     ianaparam  = iana-token "=" param-value *("," param-value)

     xparam     =x-name "=" param-value *("," param-value)

13.  Value Data Types

   The properties and parameters in MAY occur more than once

                    (";" xparam)

                    )

   Example: The following is an iCalendar object are strongly
   typed. example of this property:

       ORGANIZER;CN=John Smith:MAILTO:jsmith@host1.com

      The definition following is an example of each this property or parameter restricts the
   value with a pointer to be one of the value data types, or simply value types,
   defined in this section.  The value type will either be specified
   implicitly as the default value type or will be explicitly specified
      directory information associated with the "VALUE" parameter.  If the value type organizer:

       ORGANIZER;CN=JohnSmith;DIR="ldap://host.com:6666/o=3DDC%20Associ
        ates,c=3DUS??(cn=3DJohn%20Smith)":MAILTO:jsmith@host1.com

      The following is one an example of this property used by another
      calendar user who is acting on behalf of the
   alternate valid types, then it MUST be explicitly specified organizer, with
      responses intended to be sent back to the
   "VALUE" parameter.

13.1.  Binary

   Value organizer, not the other
      calendar user:

       ORGANIZER;SENT-BY="MAILTO:jane_doe@host.com":
        MAILTO:jsmith@host1.com

3.8.4.4.  Recurrence ID

   Property Name: BINARY RECURRENCE-ID

   Purpose: This value type property is used in conjunction with the "UID" and
      "SEQUENCE" property to identify properties that contain a character encoding of inline binary data.  For example, an
      inline attachment specific instance of an object code might be included in an
      iCalendar object.

   Description: Property values with this a recurring
      "VEVENT", "VTODO" or "VJOURNAL" calendar component.  The property
      value type MUST also include is the inline encoding parameter sequence effective value of ";ENCODING=BASE64".
      That is, all inline binary data MUST first be character encoded
      using the "BASE64" encoding method defined in RFC 2045 [4].  No
      additional content "DTSTART" property of the
      recurrence instance.

   Value Type: The default value encoding (i.e., BACKSLASH character
      encoding) type for this property is DATE-TIME.
      The time format can be any of the valid forms defined for this a DATE-
      TIME value type.

   Formal Definition: The  See DATE-TIME value type is defined by definition for specific
      interpretations of the following
   notation:

        binary     = *(4b-char) [b-end]
        ; A "BASE64" encoded character string, as defined by [RFC 2045].

        b-end      = (2b-char "==") / (3b-char "=")

        b-char = ALPHA / DIGIT / "+" / "/"

   Example: various forms.  The following is an abridged example of a "BASE64" encoded
   binary value data.

        ATTACH;VALUE=BINARY;ENCODING=BASE64:MIICajCCAdOgAwIBAgICBEUwDQY
         JKoZIhvcNAQEEBQAwdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlI
         ENvbW11bmljYXRpb25zIENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZv
           [...remainder of "BASE64" encoded binary data...]

13.2.  Boolean

   Value Name: BOOLEAN

   Purpose: This value type is used can be set
      to identify properties that contain
      either a "TRUE" or "FALSE" Boolean value.

   Description: These values are case insensitive text.  No additional
      content DATE.

   Property Parameters: Non-standard property, value encoding (i.e., BACKSLASH character encoding) is
      defined for data type, time
      zone identifier and recurrence identifier range parameters can be
      specified on this value type.

   Formal Definition: property.

   Conformance: This property can be specified in an iCalendar object
      containing a recurring calendar component.

   Description: The value type full range of calendar components specified by a
      recurrence set is defined referenced by referring to just the following
   notation:

       boolean    = "TRUE" / "FALSE"

   Example: "UID"
      property value corresponding to the calendar component.  The following is
      "RECURRENCE-ID" property allows the reference to an example individual
      instance within the recurrence set.

      If the value of a hypothetical the "DTSTART" property that
   has is a BOOLEAN DATE type value, then
      the value type:

      GIBBERISH:TRUE

13.3.  Calendar User Address

   Value Name: CAL-ADDRESS

   Purpose: This MUST be the calendar date for the recurrence instance.

      The date/time value type is used set to identify properties the time when the original
      recurrence instance would occur; meaning that contain if the intent is to
      change a calendar user address.

   Description: Friday meeting to Thursday, the date/time is still set to
      the original Friday meeting.

      The value "RECURRENCE-ID" property is used in conjunction with the "UID"
      and "SEQUENCE" property to identify a URI as defined by [RFC 1738] particular instance of a
      recurring event, to-do or any other
   IANA registered form journal.  For a given pair of "UID" and
      "SEQUENCE" property values, the "RECURRENCE-ID" value for a URI.
      recurrence instance is fixed.  When used to address an Internet
   email transport address the definition of the
      recurrence set for a calendar user, component changes, and hence the
      "SEQUENCE" property value MUST be changes, the "RECURRENCE-ID" for a
   MAILTO URI, as defined given
      recurrence instance might also change.The "RANGE" parameter is
      used to specify the effective range of recurrence instances from
      the instance specified by [RFC 1738].  No additional content the "RECURRENCE-ID" property value.  The
      default value
   encoding (i.e., BACKSLASH character encoding) for the range parameter is the single recurrence
      instance only.  The value can also be "THISANDPRIOR" to indicate a
      range defined for this by the given recurrence instance and all prior
      instances or the value type.

   Formal can be "THISANDFUTURE" to indicate a range
      defined by the given recurrence instance and all subsequent
      instances.

   Format Definition: The value type property is as defined by the following notation:

        cal-address

         recurid    = uri

   Example:

        ATTENDEE:MAILTO:jane_doe@host.com

   Figure 242

13.4.  Date

   Value Name: DATE

   Purpose: This value type is used to identify values that contain "RECURRENCE-ID" ridparam ":" ridval CRLF

         ridparam   = *(

                    ; the following are optional,
                    ; but MUST NOT occur more than once

                    (";" "VALUE" "=" ("DATE-TIME" / "DATE)) /
                    (";" tzidparam) / (";" rangeparam) /

                    ; the following is optional,
                    ; and MAY occur more than once

                    (";" xparam)

                    )

         ridval     = date-time / date
         ;Value MUST match value type

   Example: The following are examples of this property:

         RECURRENCE-ID;VALUE=DATE:19960401

         RECURRENCE-ID;RANGE=THISANDFUTURE:19960120T120000Z

3.8.4.5.  Related To

   Property Name: RELATED-TO

   Purpose: The property is used to represent a relationship or
      reference between one calendar date. component and another.

   Value Type: TEXT

   Property Parameters: Non-standard and relationship type property
      parameters can be specified on this property.

   Conformance: The property can be specified one or more times in the
      "VEVENT", "VTODO" or "VJOURNAL" calendar components.

   Description: If The property value consists of the persistent, globally
      unique identifier of another calendar component.  This value would
      be represented in a calendar component by the "UID" property.

      By default, the property permits, multiple "date" values are
   specified as value points to another calendar
      component that has a COMMA character (US-ASCII decimal 44) separated list
   of values. PARENT relationship to the referencing
      object.  The format for "RELTYPE" property parameter is used to either
      explicitly state the value default PARENT relationship type to the
      referenced calendar component or to override the default PARENT
      relationship type and specify either a CHILD or SIBLING
      relationship.  The PARENT relationship indicates that the calendar
      component is expressed as a subordinate of the referenced calendar component.
      The CHILD relationship indicates that the calendar component is a
      superior of the referenced calendar component.  The SIBLING
      relationship indicates that the calendar component is a peer of
      the referenced calendar component.

      Changes to a calendar component referenced by this property can
      have an implicit impact on the related calendar component.  For
      example, if a group event changes its start or end date or time,
      then the related, dependent events will need to have their start
      and end dates changed in a corresponding way.  Similarly, if a
      PARENT calendar component is canceled or deleted, then there is an
      implied impact to the related CHILD calendar components.  This
      property is intended only to provide information on the
      relationship of calendar components.  It is up to the target
      calendar system to maintain any property implications of this
      relationship.

   Format Definition: The property is defined by the following notation:

         related    = "RELATED-TO" [relparam] ":" text CRLF

         relparam   = *(

                    ; the following is optional,
                    ; but MUST NOT occur more than once

                    (";" reltypeparam) /

                    ; the following is optional,
                    ; and MAY occur more than once

                    (";" xparm)

                    )

      The following is an example of this property:

         RELATED-TO:<jsmith.part7.19960817T083000.xyzMail@host3.com>

         RELATED-TO:<19960401-080045-4000F192713-0052@host1.com>

3.8.4.6.  Uniform Resource Locator

   Property Name: URL

   Purpose: This property defines a Uniform Resource Locator (URL)
      associated with the iCalendar object.

   Value Type: URI

   Property Parameters: Non-standard property parameters can be
      specified on this property.

   Conformance: This property can be specified once in the "VEVENT",
      "VTODO", "VJOURNAL" or "VFREEBUSY" calendar components.

   Description: This property may be used in a calendar component to
      convey a location where a more dynamic rendition of the calendar
      information associated with the calendar component can be found.
      This memo does not attempt to standardize the form of the URI, nor
      the format of the resource pointed to by the property value.  If
      the URL property and Content-Location MIME header are both
      specified, they MUST point to the same resource.

   Format Definition: The property is defined by the following notation:

         url        = "URL" urlparam ":" uri CRLF

         urlparam   = *(";" xparam)

   Example: The following is an example of this property:

         URL:http://abc.com/pub/calendars/jsmith/mytime.ics

3.8.4.7.  Unique Identifier

   Property Name: UID

   Purpose: This property defines the persistent, globally unique
      identifier for the calendar component.

   Value Type: TEXT

   Property Parameters: Non-standard property parameters can be
      specified on this property.

   Conformance: The property MUST be specified in the "VEVENT", "VTODO",
      "VJOURNAL" or "VFREEBUSY" calendar components.

   Description: The UID itself MUST be a globally unique identifier.
      The generator of the identifier MUST guarantee that the identifier
      is unique.  There are several algorithms that can be used to
      accomplish this.  The identifier is RECOMMENDED to be the
      identical syntax to the [RFC0822] addr-spec.  A good method to
      assure uniqueness is to put the domain name or a domain literal IP
      address of the host on which the identifier was created on the
      right hand side of the "@", and on the left hand side, put a
      combination of the current calendar date and time of day (i.e.,
      formatted in as a DATE-TIME value) along with some other currently
      unique (perhaps sequential) identifier available on the system
      (for example, a process id number).  Using a date/time value on
      the left hand side and a domain name or domain literal on the
      right hand side makes it possible to guarantee uniqueness since no
      two hosts should be using the same domain name or IP address at
      the same time.  Though other algorithms will work, it is
      RECOMMENDED that the right hand side contain some domain
      identifier (either of the host itself or otherwise) such that the
      generator of the message identifier can guarantee the uniqueness
      of the left hand side within the scope of that domain.

      This is the method for correlating scheduling messages with the
      referenced "VEVENT", "VTODO", or "VJOURNAL" calendar component.

      The full range of calendar components specified by a recurrence
      set is referenced by referring to just the "UID" property value
      corresponding to the calendar component.  The "RECURRENCE-ID"
      property allows the reference to an individual instance within the
      recurrence set.

      This property is an important method for group scheduling
      applications to match requests with later replies, modifications
      or deletion requests.  Calendaring and scheduling applications
      MUST generate this property in "VEVENT", "VTODO" and "VJOURNAL"
      calendar components to assure interoperability with other group
      scheduling applications.  This identifier is created by the
      calendar system that generates an iCalendar object.

      Implementations MUST be able to receive and persist values of at
      least 255 characters for this property.

   Format Definition: The property is defined by the following notation:

         uid        = "UID" uidparam ":" text CRLF
         uidparam   = *(";" xparam)

   Example: The following is an example of this property:

         UID:19960401T080045Z-4000F192713-0052@host1.com

3.8.5.  Recurrence Component Properties

   The following properties specify recurrence information in calendar
   components.

3.8.5.1.  Exception Date/Times

   Property Name: EXDATE

   Purpose: This property defines the list of date/time exceptions for a
      recurring calendar component.

   Value Type: The default value type for this property is DATE-TIME.
      The value type can be set to DATE.

   Property Parameters: Non-standard, value data type and time zone
      identifier property parameters can be specified on this property.

   Conformance: This property can be specified in an iCalendar object
      that includes a recurring calendar component.

   Description: The exception dates, if specified, are used in computing
      the recurrence set.  The recurrence set is the complete set of
      recurrence instances for a calendar component.  The recurrence set
      is generated by considering the initial "DTSTART" property along
      with the "RRULE", "RDATE", "EXDATE" and "EXRULE" properties
      contained within the iCalendar object.  The "DTSTART" property
      defines the first instance in the recurrence set.  Multiple
      instances of the "RRULE" and "EXRULE" properties can also be
      specified to define more sophisticated recurrence sets.  The final
      recurrence set is generated by gathering all of the start date-
      times generated by any of the specified "RRULE" and "RDATE"
      properties, and then excluding any start date and times which fall
      within the union of start date and times generated by any
      specified "EXRULE" and "EXDATE" properties.  This implies that
      start date and times within exclusion related properties (i.e.,
      "EXDATE" and "EXRULE") take precedence over those specified by
      inclusion properties (i.e., "RDATE" and "RRULE").  Where duplicate
      instances are generated by the "RRULE" and "RDATE" properties,
      only one recurrence is considered.  Duplicate instances are
      ignored.

      The "EXDATE" property can be used to exclude the value specified
      in "DTSTART".  However, in such cases the original "DTSTART" date
      MUST still be maintained by the calendaring and scheduling system
      because the original "DTSTART" value has inherent usage
      dependencies by other properties such as the "RECURRENCE-ID".

   Format Definition: The property is defined by the following notation:

         exdate     = "EXDATE" exdtparam ":" exdtval *("," exdtval) CRLF

         exdtparam  = *(

                    ; the following are optional,
                    ; but MUST NOT occur more than once

                    (";" "VALUE" "=" ("DATE-TIME" / "DATE")) /

                    (";" tzidparam) /

                    ; the following is optional,
                    ; and MAY occur more than once

                    (";" xparam)

                    )

         exdtval    = date-time / date
         ;Value MUST match value type

   Example: The following is an example of this property:

         EXDATE:19960402T010000Z,19960403T010000Z,19960404T010000Z

3.8.5.2.  Exception Rule

   Property Name: EXRULE

   Purpose: This property defines a rule or repeating pattern for an
      exception to a recurrence set.

   Value Type: RECUR

   Property Parameters: Non-standard property parameters can be
      specified on this property.

   Conformance: This property can be specified in "VEVENT", "VTODO" or
      "VJOURNAL" calendar components.

   Description: The exception rule, if specified, is used in computing
      the recurrence set.  The recurrence set is the complete set of
      recurrence instances for a calendar component.  The recurrence set
      is generated by considering the initial "DTSTART" property along
      with the "RRULE", "RDATE", "EXDATE" and "EXRULE" properties
      contained within the iCalendar object.  The "DTSTART" defines the
      first instance in the recurrence set.  Multiple instances of the
      "RRULE" and "EXRULE" properties can also be specified to define
      more sophisticated recurrence sets.  The final recurrence set is
      generated by gathering all of the start date-times generated by
      any of the specified "RRULE" and "RDATE" properties, and excluding
      any start date and times which fall within the union of start date
      and times generated by any specified "EXRULE" and "EXDATE"
      properties.  This implies that start date and times within
      exclusion related properties (i.e., "EXDATE" and "EXRULE") take
      precedence over those specified by inclusion properties (i.e.,
      "RDATE" and "RRULE").  Where duplicate instances are generated by
      the "RRULE" and "RDATE" properties, only one recurrence is
      considered.  Duplicate instances are ignored.

      The "EXRULE" property can be used to exclude the value specified
      in "DTSTART".  However, in such cases the original "DTSTART" date
      MUST still be maintained by the calendaring and scheduling system
      because the original "DTSTART" value has inherent usage
      dependencies by other properties such as the "RECURRENCE-ID".

   Format Definition: The property is defined by the following notation:

         exrule     = "EXRULE" exrparam ":" recur CRLF

         exrparam   = *(";" xparam)

   Example: The following are examples of this property.  Except every
      other week, on Tuesday and Thursday for 4 occurrences:

         EXRULE:FREQ=WEEKLY;COUNT=4;INTERVAL=2;BYDAY=TU,TH

      Except daily for 10 occurrences:

         EXRULE:FREQ=DAILY;COUNT=10
      Except yearly in June and July for 8 occurrences:

         EXRULE:FREQ=YEARLY;COUNT=8;BYMONTH=6,7

3.8.5.3.  Recurrence Date/Times

   Property Name: RDATE

   Purpose: This property defines the list of date/times for a
      recurrence set.

   Value Type: The default value type for this property is DATE-TIME.
      The value type can be set to DATE or PERIOD.

   Property Parameters: Non-standard, value data type and time zone
      identifier property parameters can be specified on this property.

   Conformance: The property can be specified in "VEVENT", "VTODO",
      "VJOURNAL" or "VTIMEZONE" calendar components.

   Description: This property can appear along with the "RRULE" property
      to define an aggregate set of repeating occurrences.  When they
      both appear in an iCalendar object, the recurring events are
      defined by the union of occurrences defined by both the "RDATE"
      and "RRULE".

      The recurrence dates, if specified, are used in computing the
      recurrence set.  The recurrence set is the complete set of
      recurrence instances for a calendar component.  The recurrence set
      is generated by considering the initial "DTSTART" property along
      with the "RRULE", "RDATE", "EXDATE" and "EXRULE" properties
      contained within the iCalendar object.  The "DTSTART" property
      defines the first instance in the recurrence set.  Multiple
      instances of the "RRULE" and "EXRULE" properties can also be
      specified to define more sophisticated recurrence sets.  The final
      recurrence set is generated by gathering all of the start date/
      times generated by any of the specified "RRULE" and "RDATE"
      properties, and excluding any start date/times which fall within
      the union of start date/times generated by any specified "EXRULE"
      and "EXDATE" properties.  This implies that start date/times
      within exclusion related properties (i.e., "EXDATE" and "EXRULE")
      take precedence over those specified by inclusion properties
      (i.e., "RDATE" and "RRULE").  Where duplicate instances are
      generated by the "RRULE" and "RDATE" properties, only one
      recurrence is considered.  Duplicate instances are ignored.

   Format Definition: The property is defined by the following notation:

     rdate      = "RDATE" rdtparam ":" rdtval *("," rdtval) CRLF

     rdtparam   = *(

                ; the following are optional,
                ; but MUST NOT occur more than once

                (";" "VALUE" "=" ("DATE-TIME" / "DATE" / "PERIOD")) /
                (";" tzidparam) /

                ; the following is optional,
                ; and MAY occur more than once

                (";" xparam)

                )

     rdtval     = date-time / date / period
     ;Value MUST match value type

   Example: The following are examples of this property:

         RDATE:19970714T123000Z

         RDATE;TZID=US-EASTERN:19970714T083000

         RDATE;VALUE=PERIOD:19960403T020000Z/19960403T040000Z,
          19960404T010000Z/PT3H

         RDATE;VALUE=DATE:19970101,19970120,19970217,19970421
          19970526,19970704,19970901,19971014,19971128,19971129,19971225

3.8.5.4.  Recurrence Rule

   Property Name: RRULE

   Purpose: This property defines a rule or repeating pattern for
      recurring events, to-dos, or time zone definitions.

   Value Type: RECUR

   Property Parameters: Non-standard property parameters can be
      specified on this property.

   Conformance: This property can be specified one or more times in
      recurring "VEVENT", "VTODO" and "VJOURNAL" calendar components.
      It can also be specified once in each STANDARD or DAYLIGHT sub-
      component of the "VTIMEZONE" calendar component.

   Description: The recurrence rule, if specified, is used in computing
      the recurrence set.  The recurrence set is the complete set of
      recurrence instances for a calendar component.  The recurrence set
      is generated by considering the initial "DTSTART" property along
      with the "RRULE", "RDATE", "EXDATE" and "EXRULE" properties
      contained within the iCalendar object.  The "DTSTART" property
      defines the first instance in the recurrence set.  Multiple
      instances of the "RRULE" and "EXRULE" properties can also be
      specified to define more sophisticated recurrence sets.  The final
      recurrence set is generated by gathering all of the start date/
      times generated by any of the specified "RRULE" and "RDATE"
      properties, and excluding any start date/times which fall within
      the union of start date/times generated by any specified "EXRULE"
      and "EXDATE" properties.  This implies that start date/times
      within exclusion related properties (i.e., "EXDATE" and "EXRULE")
      take precedence over those specified by inclusion properties
      (i.e., "RDATE" and "RRULE").  Where duplicate instances are
      generated by the "RRULE" and "RDATE" properties, only one
      recurrence is considered.  Duplicate instances are ignored.

      The "DTSTART" and "DTEND" property pair or "DTSTART" and
      "DURATION" property pair, specified within the iCalendar object
      defines the first instance of the recurrence.  When used with a
      recurrence rule, the "DTSTART" and "DTEND" properties MUST be
      specified in local time and the appropriate set of "VTIMEZONE"
      calendar components MUST be included.  For detail on the usage of
      the "VTIMEZONE" calendar component, see the "VTIMEZONE" calendar
      component definition.

      Any duration associated with the iCalendar object applies to all
      members of the generated recurrence set.  Any modified duration
      for specific recurrences MUST be explicitly specified using the
      "RDATE" property.

   Format Definition: The property is defined by the following notation:

         rrule      = "RRULE" rrulparam ":" recur CRLF

         rrulparam  = *(";" xparam)
   Example: All examples assume the Eastern United States time zone.

      Daily for 10 occurrences:

         DTSTART;TZID=US-Eastern:19970902T090000
         RRULE:FREQ=DAILY;COUNT=10

         ==> (1997 9:00 AM EDT)September 2-11

      Daily until December 24, 1997:

         DTSTART;TZID=US-Eastern:19970902T090000
         RRULE:FREQ=DAILY;UNTIL=19971224T000000Z

         ==> (1997 9:00 AM EDT)September 2-30;October 1-25
             (1997 9:00 AM EST)October 26-31;November 1-30;December 1-23

      Every other day - forever:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=DAILY;INTERVAL=2

     ==> (1997 9:00 AM EDT)September2,4,6,8...24,26,28,30;
          October 2,4,6...20,22,24
         (1997 9:00 AM EST)October 26,28,30;November 1,3,5,7...25,27,29;
          Dec 1,3,...

      Every 10 days, 5 occurrences:

         DTSTART;TZID=US-Eastern:19970902T090000
         RRULE:FREQ=DAILY;INTERVAL=10;COUNT=5

         ==> (1997 9:00 AM EDT)September 2,12,22;October 2,12

      Everyday in January, for 3 years:

         DTSTART;TZID=US-Eastern:19980101T090000
         RRULE:FREQ=YEARLY;UNTIL=20000131T090000Z;
          BYMONTH=1;BYDAY=SU,MO,TU,WE,TH,FR,SA
         or
         RRULE:FREQ=DAILY;UNTIL=20000131T090000Z;BYMONTH=1

         ==> (1998 9:00 AM EDT)January 1-31
             (1999 9:00 AM EDT)January 1-31
             (2000 9:00 AM EDT)January 1-31
      Weekly for 10 occurrences

         DTSTART;TZID=US-Eastern:19970902T090000
         RRULE:FREQ=WEEKLY;COUNT=10

         ==> (1997 9:00 AM EDT)September 2,9,16,23,30;October 7,14,21
             (1997 9:00 AM EST)October 28;November 4

      Weekly until December 24, 1997

         DTSTART;TZID=US-Eastern:19970902T090000
         RRULE:FREQ=WEEKLY;UNTIL=19971224T000000Z

         ==> (1997 9:00 AM EDT)September 2,9,16,23,30;October 7,14,21
             (1997 9:00 AM EST)October 28;November 4,11,18,25;
                               December 2,9,16,23

      Every other week - forever:

         DTSTART;TZID=US-Eastern:19970902T090000
         RRULE:FREQ=WEEKLY;INTERVAL=2;WKST=SU

         ==> (1997 9:00 AM EDT)September 2,16,30;October 14
             (1997 9:00 AM EST)October 28;November 11,25;December 9,23
             (1998 9:00 AM EST)January 6,20;February
         ...

      Weekly on Tuesday and Thursday for 5 weeks:

      DTSTART;TZID=US-Eastern:19970902T090000
      RRULE:FREQ=WEEKLY;UNTIL=19971007T000000Z;WKST=SU;BYDAY=TU,TH
      or

      RRULE:FREQ=WEEKLY;COUNT=10;WKST=SU;BYDAY=TU,TH

      ==> (1997 9:00 AM EDT)September 2,4,9,11,16,18,23,25,30;October 2

      Every other week on Monday, Wednesday and Friday until December
      24, 1997, but starting on Tuesday, September 2, 1997:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=WEEKLY;INTERVAL=2;UNTIL=19971224T000000Z;WKST=SU;
      BYDAY=MO,WE,FR

     ==> (1997 9:00 AM EDT)September 2,3,5,15,17,19,29;October
     1,3,13,15,17
         (1997 9:00 AM EST)October 27,29,31;November 10,12,14,24,26,28;
                           December 8,10,12,22
      Every other week on Tuesday and Thursday, for 8 occurrences:

         DTSTART;TZID=US-Eastern:19970902T090000
         RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=8;WKST=SU;BYDAY=TU,TH

         ==> (1997 9:00 AM EDT)September 2,4,16,18,30;October 2,14,16

      Monthly on the 1st Friday for ten occurrences:

         DTSTART;TZID=US-Eastern:19970905T090000
         RRULE:FREQ=MONTHLY;COUNT=10;BYDAY=1FR

         ==> (1997 9:00 AM EDT)September 5;October 3
             (1997 9:00 AM EST)November 7;Dec 5
             (1998 9:00 AM EST)January 2;February 6;March 6;April 3
             (1998 9:00 AM EDT)May 1;June 5

      Monthly on the 1st Friday until December 24, 1997:

         DTSTART;TZID=US-Eastern:19970905T090000
         RRULE:FREQ=MONTHLY;UNTIL=19971224T000000Z;BYDAY=1FR

         ==> (1997 9:00 AM EDT)September 5;October 3
             (1997 9:00 AM EST)November 7;December 5

      Every other month on the 1st and last Sunday of the month for 10
      occurrences:

         DTSTART;TZID=US-Eastern:19970907T090000
         RRULE:FREQ=MONTHLY;INTERVAL=2;COUNT=10;BYDAY=1SU,-1SU

         ==> (1997 9:00 AM EDT)September 7,28
             (1997 9:00 AM EST)November 2,30
             (1998 9:00 AM EST)January 4,25;March 1,29
             (1998 9:00 AM EDT)May 3,31

      Monthly on the second to last Monday of the month for 6 months:

         DTSTART;TZID=US-Eastern:19970922T090000
         RRULE:FREQ=MONTHLY;COUNT=6;BYDAY=-2MO

         ==> (1997 9:00 AM EDT)September 22;October 20
             (1997 9:00 AM EST)November 17;December 22
             (1998 9:00 AM EST)January 19;February 16
      Monthly on the third to the last day of the month, forever:

         DTSTART;TZID=US-Eastern:19970928T090000
         RRULE:FREQ=MONTHLY;BYMONTHDAY=-3

         ==> (1997 9:00 AM EDT)September 28
             (1997 9:00 AM EST)October 29;November 28;December 29
             (1998 9:00 AM EST)January 29;February 26
         ...

      Monthly on the 2nd and 15th of the month for 10 occurrences:

         DTSTART;TZID=US-Eastern:19970902T090000
         RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=2,15

         ==> (1997 9:00 AM EDT)September 2,15;October 2,15
             (1997 9:00 AM EST)November 2,15;December 2,15
             (1998 9:00 AM EST)January 2,15

      Monthly on the first and last day of the month for 10 occurrences:

         DTSTART;TZID=US-Eastern:19970930T090000
         RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=1,-1

         ==> (1997 9:00 AM EDT)September 30;October 1
             (1997 9:00 AM EST)October 31;November 1,30;December 1,31
             (1998 9:00 AM EST)January 1,31;February 1

      Every 18 months on the 10th thru 15th of the month for 10
      occurrences:

     DTSTART;TZID=US-Eastern:19970910T090000
     RRULE:FREQ=MONTHLY;INTERVAL=18;COUNT=10;BYMONTHDAY=10,11,12,13,14,
      15

     ==> (1997 9:00 AM EDT)September 10,11,12,13,14,15
         (1999 9:00 AM EST)March 10,11,12,13

      Every Tuesday, every other month:

         DTSTART;TZID=US-Eastern:19970902T090000
         RRULE:FREQ=MONTHLY;INTERVAL=2;BYDAY=TU

         ==> (1997 9:00 AM EDT)September 2,9,16,23,30
             (1997 9:00 AM EST)November 4,11,18,25
             (1998 9:00 AM EST)January 6,13,20,27;March 3,10,17,24,31
         ...

      Yearly in June and July for 10 occurrences:

       DTSTART;TZID=US-Eastern:19970610T090000
       RRULE:FREQ=YEARLY;COUNT=10;BYMONTH=6,7
       ==> (1997 9:00 AM EDT)June 10;July 10
           (1998 9:00 AM EDT)June 10;July 10
           (1999 9:00 AM EDT)June 10;July 10
           (2000 9:00 AM EDT)June 10;July 10
           (2001 9:00 AM EDT)June 10;July 10
       Note: Since none of the BYDAY, BYMONTHDAY or BYYEARDAY components
       are specified, the day is gotten from DTSTART

      Every other year on January, February, and March for 10
      occurrences:

         DTSTART;TZID=US-Eastern:19970310T090000
         RRULE:FREQ=YEARLY;INTERVAL=2;COUNT=10;BYMONTH=1,2,3

         ==> (1997 9:00 AM EST)March 10
             (1999 9:00 AM EST)January 10;February 10;March 10
             (2001 9:00 AM EST)January 10;February 10;March 10
             (2003 9:00 AM EST)January 10;February 10;March 10

      Every 3rd year on the 1st, 100th and 200th day for 10 occurrences:

         DTSTART;TZID=US-Eastern:19970101T090000
         RRULE:FREQ=YEARLY;INTERVAL=3;COUNT=10;BYYEARDAY=1,100,200

         ==> (1997 9:00 AM EST)January 1
             (1997 9:00 AM EDT)April 10;July 19
             (2000 9:00 AM EST)January 1
             (2000 9:00 AM EDT)April 9;July 18
             (2003 9:00 AM EST)January 1
             (2003 9:00 AM EDT)April 10;July 19
             (2006 9:00 AM EST)January 1

      Every 20th Monday of the year, forever:

         DTSTART;TZID=US-Eastern:19970519T090000
         RRULE:FREQ=YEARLY;BYDAY=20MO

         ==> (1997 9:00 AM EDT)May 19
             (1998 9:00 AM EDT)May 18
             (1999 9:00 AM EDT)May 17
         ...

      Monday of week number 20 (where the default start of the week is
      Monday), forever:

         DTSTART;TZID=US-Eastern:19970512T090000
         RRULE:FREQ=YEARLY;BYWEEKNO=20;BYDAY=MO

         ==> (1997 9:00 AM EDT)May 12
             (1998 9:00 AM EDT)May 11
             (1999 9:00 AM EDT)May 17
         ...

      Every Thursday in March, forever:

         DTSTART;TZID=US-Eastern:19970313T090000
         RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=TH

         ==> (1997 9:00 AM EST)March 13,20,27
             (1998 9:00 AM EST)March 5,12,19,26
             (1999 9:00 AM EST)March 4,11,18,25
         ...

      Every Thursday, but only during June, July, and August, forever:

         DTSTART;TZID=US-Eastern:19970605T090000
         RRULE:FREQ=YEARLY;BYDAY=TH;BYMONTH=6,7,8

         ==> (1997 9:00 AM EDT)June 5,12,19,26;July 3,10,17,24,31;
                           August 7,14,21,28
             (1998 9:00 AM EDT)June 4,11,18,25;July 2,9,16,23,30;
                           August 6,13,20,27
             (1999 9:00 AM EDT)June 3,10,17,24;July 1,8,15,22,29;
                           August 5,12,19,26
         ...

      Every Friday the 13th, forever:

         DTSTART;TZID=US-Eastern:19970902T090000
         EXDATE;TZID=US-Eastern:19970902T090000
         RRULE:FREQ=MONTHLY;BYDAY=FR;BYMONTHDAY=13

         ==> (1998 9:00 AM EST)February 13;March 13;November 13
             (1999 9:00 AM EDT)August 13
             (2000 9:00 AM EDT)October 13
         ...

      The first Saturday that follows the first Sunday of the month,
      forever:

         DTSTART;TZID=US-Eastern:19970913T090000
         RRULE:FREQ=MONTHLY;BYDAY=SA;BYMONTHDAY=7,8,9,10,11,12,13

         ==> (1997 9:00 AM EDT)September 13;October 11
             (1997 9:00 AM EST)November 8;December 13
             (1998 9:00 AM EST)January 10;February 7;March 7
             (1998 9:00 AM EDT)April 11;May 9;June 13...
         ...

      Every four years, the [ISO
   8601] complete representation, basic format for first Tuesday after a calendar date. Monday in November,
      forever (U.S. Presidential Election day):

     DTSTART;TZID=US-Eastern:19961105T090000
     RRULE:FREQ=YEARLY;INTERVAL=4;BYMONTH=11;BYDAY=TU;BYMONTHDAY=2,3,4,
      5,6,7,8

     ==> (1996 9:00 AM EST)November 5
         (2000 9:00 AM EST)November 7
         (2004 9:00 AM EST)November 2
     ...

      The
   textual format specifies a four-digit year, two-digit month, and two-
   digit day of the month.  There are no separator characters between 3rd instance into the year, month and day component text.

   No additional content value encoding (i.e., BACKSLASH character
   encoding) is defined of one of Tuesday, Wednesday or
      Thursday, for this value type.

   Formal Definition: The value type is defined by the following
   notation:

        date               = date-value

        date-value         = date-fullyear date-month date-mday
        date-fullyear      = 4DIGIT

        date-month         = 2DIGIT        ;01-12
        date-mday          = 2DIGIT        ;01-28, 01-29, 01-30, 01-31
                                           ;based on month/year

   Example: next 3 months:

         DTSTART;TZID=US-Eastern:19970904T090000
         RRULE:FREQ=MONTHLY;COUNT=3;BYDAY=TU,WE,TH;BYSETPOS=3

         ==> (1997 9:00 AM EDT)September 4;October 7
             (1997 9:00 AM EST)November 6

      The following represents July 14, 1997:

        19970714

   Figure 244

13.5.  Date-Time

   Value Name: DATE-TIME

   Purpose: This value type is used 2nd to identify values that specify a
   precise calendar date and time last weekday of day.

   Description: If the property permits, multiple "date-time" values are
   specified as a COMMA character (US-ASCII decimal 44) separated list
   of values.  No additional content value encoding (i.e., BACKSLASH
   character encoding) is defined for this value type.

   The "DATE-TIME" data type is used month:

         DTSTART;TZID=US-Eastern:19970929T090000
         RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-2

         ==> (1997 9:00 AM EDT)September 29
             (1997 9:00 AM EST)October 30;November 27;December 30
             (1998 9:00 AM EST)January 29;February 26;March 30
         ...

      Every 3 hours from 9:00 AM to identify values that contain a
   precise calendar date and time of day.  The format is based 5:00 PM on the
   [ISO 8601] complete representation, basic format for a calendar date specific day:

         DTSTART;TZID=US-Eastern:19970902T090000
         RRULE:FREQ=HOURLY;INTERVAL=3;UNTIL=19970902T170000Z
         ==> (September 2, 1997 EDT)09:00,12:00,15:00

      Every 15 minutes for 6 occurrences:

         DTSTART;TZID=US-Eastern:19970902T090000
         RRULE:FREQ=MINUTELY;INTERVAL=15;COUNT=6

         ==> (September 2, 1997 EDT)09:00,09:15,09:30,09:45,10:00,10:15

      Every hour and time of day.  The text format is a concatenation of the "date",
   followed by the LATIN CAPITAL LETTER T character (US-ASCII decimal
   84) time designator, followed by the "time" format.

   The "DATE-TIME" data type expresses time values in three forms:

   The form of date and time with UTC offset MUST NOT be used.  For
   example, the following is not valid half for a date-time value:

   DTSTART:19980119T230000-0800 ;Invalid time format

   FORM #1: DATE WITH LOCAL TIME

   The date with local time form is simply a date-time value that does
   not contain the UTC designator nor does it reference a time zone.
   For example, the following represents Janurary 18, 1998, at 11 PM:

   DTSTART:19980118T230000

   Date-time values of this type are said to be "floating" and are not
   bound to any time zone in particular.  They are used 4 occurrences:

         DTSTART;TZID=US-Eastern:19970902T090000
         RRULE:FREQ=MINUTELY;INTERVAL=90;COUNT=4

         ==> (September 2, 1997 EDT)09:00,10:30;12:00;13:30

      Every 20 minutes from 9:00 AM to represent 4:40 PM every day:

         DTSTART;TZID=US-Eastern:19970902T090000
         RRULE:FREQ=DAILY;BYHOUR=9,10,11,12,13,14,15,16;BYMINUTE=0,20,40
         or
         RRULE:FREQ=MINUTELY;INTERVAL=20;BYHOUR=9,10,11,12,13,14,15,16

         ==> (September 2, 1997 EDT)9:00,9:20,9:40,10:00,10:20,
                                    ... 16:00,16:20,16:40
             (September 3, 1997 EDT)9:00,9:20,9:40,10:00,10:20,
                                   ...16:00,16:20,16:40
         ...

      An example where the
   same hour, minute, and second value regardless days generated makes a difference because of which time zone is
   currently being observed.  For example, an event can be defined that
   indicates that an individual will be busy
      WKST:

         DTSTART;TZID=US-Eastern:19970805T090000
         RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=MO

         ==> (1997 EDT)Aug 5,10,19,24

         changing only WKST from 11:00 AM MO to 1:00 PM
   every day, no matter which time zone SU, yields different results...

         DTSTART;TZID=US-Eastern:19970805T090000
         RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=SU
         ==> (1997 EDT)August 5,17,19,31

3.8.6.  Alarm Component Properties

   The following properties specify alarm information in calendar
   components.

3.8.6.1.  Action

   Property Name: ACTION

   Purpose: This property defines the person action to be invoked when an alarm
      is in.  In these
   cases, a local time triggered.

   Value Type: TEXT

   Property Parameters: Non-standard property parameters can be specified.  The recipient
      specified on this property.

   Conformance: This property MUST be specified once in a "VALARM"
      calendar component.

   Description: Each "VALARM" calendar component has a particular type
      of an iCalendar
   object action associated with a it.  This property value consisting of a local time, without any
   relative time zone information, SHOULD interpret the value as being
   fixed to whatever time zone specifies the ATTENDEE type of
      action

   Format Definition: The property is defined by the following notation:

       action     = "ACTION" actionparam ":" actionvalue CRLF

       actionparam        = *(";" xparam)

       actionvalue        = "AUDIO" / "DISPLAY" / "EMAIL" / "PROCEDURE"
                          / iana-token / x-name

   Example: The following are examples of this property in at any given moment. a "VALARM"
      calendar component:

         ACTION:AUDIO

         ACTION:DISPLAY

         ACTION:PROCEDURE

3.8.6.2.  Repeat Count

   Property Name: REPEAT

   Purpose: This means that two ATTENDEEs, in different property defines the number of time zones, receiving the
   same event definition as a floating time, may alarm should be participating in
      repeated, after the
   event at different actual times.  Floating time SHOULD only initial trigger.

   Value Type: INTEGER
   Property Parameters: Non-standard property parameters can be used
   where that is the reasonable behavior.

   In most cases, a fixed time is desired.  To properly communicate a
   fixed time
      specified on this property.

   Conformance: This property can be specified in a "VALARM" calendar
      component.

   Description: If the alarm triggers more than once, then this property value, either UTC time or local time with
   time zone reference
      MUST be specified.

   The use of local time in a DATE-TIME value without specified along with the TZID "DURATION" property.

   Format Definition: The property
   parameter is to be interpreted as floating time, regardless defined by the following notation:

         repeatcnt  = "REPEAT" repparam ":" integer CRLF
         ;Default is "0", zero.

         repparam   = *(";" xparam)

   Example: The following is an example of this property for an alarm
      that repeats 4 additional times with a 5 minute delay after the
   existence
      initial triggering of "VTIMEZONE" calendar components in the iCalendar object.

   FORM #2: DATE WITH UTC TIME alarm:

         REPEAT:4
         DURATION:PT5M

3.8.6.3.  Trigger

   Property Name: TRIGGER

   Purpose: This property specifies when an alarm will trigger.

   Value Type: The date with UTC time, or absolute time, default value type is identified by DURATION.  The value type can
      be set to a LATIN
   CAPITAL LETTER Z suffix character (US-ASCII decimal 90), DATE-TIME value type, in which case the value MUST
      specify a UTC
   designator, appended to the time formatted DATE-TIME value.  For example, the following
   represents January 19, 1998, at 0700 UTC:

   DTSTART:19980119T070000Z

   Property Parameters: Non-standard, value data type, time zone
      identifier or trigger relationship property parameters can be
      specified on this property.  The TZID trigger relationship property
      parameter MUST NOT only be applied to DATE-TIME
   properties whose time values are specified in UTC.

   FORM #3: DATE WITH LOCAL TIME AND TIME ZONE REFERENCE

   The date and local time with reference to time zone information when the value type is
   identified by DURATION.

   Conformance: This property MUST be specified in the use "VALARM" calendar
      component.

   Description: Within the TZID "VALARM" calendar component, this property parameter to reference
      defines when the
   appropriate alarm will trigger.  The default value type is
      DURATION, specifying a relative time zone definition.  TZID for the trigger of the alarm.
      The default duration is discussed in detail in relative to the
   section on Time Zone.  For example, start of an event or to-do
      that the following represents 2 AM in
   New York on Janurary 19, 1998:

   DTSTART;TZID=US-Eastern:19980119T020000

   Example: alarm is associated with.  The following represents July 14, 1997, at 1:30 PM in New
   York City in each duration can be explicitly
      set to trigger from either the end or the start of the three time formats, using associated
      event or to-do with the "DTSTART"
   property.

        DTSTART:19970714T133000            ;Local time
        DTSTART:19970714T173000Z           ;UTC time
        DTSTART;TZID=US-Eastern:19970714T133000    ;Local time and time
                           ; zone reference

   Figure 245 "RELATED" parameter.  A time value MUST ONLY specify 60 seconds when specifying of START
      will set the
   periodic "leap second" in alarm to trigger off the time value.  For example:

        COMPLETED:19970630T235960Z

13.6.  Duration

   Value Name: DURATION

   Purpose: This start of the associated
      event or to-do.  A value type is used of END will set the alarm to identify properties that contain
   a duration trigger off
      the end of time.

   Description: If the property permits, multiple "duration" values are associated event or to-do.

      Either a positive or negative duration may be specified by for the
      "TRIGGER" property.  An alarm with a COMMA character (US-ASCII decimal 44) separated list
   of values.  The format positive duration is expressed as
      triggered after the [ISO 8601] basic format
   for associated start or end of the event or to-do.
      An alarm with a negative duration is triggered before the
      associated start or end of time.  The format can represent durations in
   terms of weeks, days, hours, minutes, and seconds.

   No additional content value encoding (i.e., BACKSLASH character
   encoding) are defined for this value type.

   Formal Definition: the event or to-do.

      The value type "RELATED" property parameter is defined by not valid if the following
   notation:

        dur-value  = (["+"] / "-") "P" (dur-date / dur-time / dur-week)

        dur-date   = dur-day [dur-time]
        dur-time   = "T" (dur-hour / dur-minute / dur-second)
        dur-week   = 1*DIGIT "W"
        dur-hour   = 1*DIGIT "H" [dur-minute]
        dur-minute = 1*DIGIT "M" [dur-second]
        dur-second = 1*DIGIT "S"
        dur-day    = 1*DIGIT "D"

   Example: A duration of 15 days, 5 hours and 20 seconds would be:

        P15DT5H0M20S

   Figure 248

   A duration of 7 weeks would be:

        P7W

13.7.  Period of Time

   Value Name: PERIOD

   Purpose: This value type of
      the property is used set to identify values that contain DATE-TIME (i.e., for an absolute date and
      time alarm trigger).  If a
   precise period value type of time.

   Description: If DATE-TIME is specified,
      then the property permits, multiple "period" values are value MUST be specified by a COMMA character (US-ASCII decimal 44) separated list
   of values.  There are two forms of a period of time.  First, a period
   of in the UTC time format.
      If an absolute trigger is identified by its start and its end.  This format specified on an alarm for a recurring
      event or to-do, then the alarm will only trigger for the specified
      absolute date/time, along with any specified repeating instances.

      If the trigger is
   expressed as set relative to START, then the "DTSTART"
      property MUST be present in the [ISO 8601] complete representation, basic format associated "VEVENT" or "VTODO"
      calendar component.  If an alarm is specified for
   "DATE-TIME" start of the period, followed by a SOLIDUS character (US-
   ASCII decimal 47), followed by an event with
      the "DATE-TIME" of trigger set relative to the end of END, then the
   period.  The start of "DTEND" property or
      the period "DSTART" and "DURATION' properties MUST be before present in the end of
      associated "VEVENT" calendar component.  If the
   period.  Second, a period of time can also be defined by a start and
   a positive duration of time.  The format alarm is expressed as the [ISO
   8601] complete representation, basic format specified
      for a to-do with a trigger set relative to the "DATE-TIME" start
   of END, then either
      the period, followed by a SOLIDUS character (US-ASCII decimal 47),
   followed by "DUE" property or the [ISO 8601] basic format for "DTSTART" and "DURATION" properties MUST
      be present in the associated "VTODO" calendar component.

      Alarms specified in an event or to-do which is defined in terms of
      a DATE value type will be triggered relative to 00:00:00 UTC on
      the period.

   Formal specified date.  For example, if "DTSTART:19980205, then the
      duration trigger will be relative to19980205T000000Z.

   Format Definition: The data type property is defined by the following notation:

        period

         trigger    = period-explicit "TRIGGER" (trigrel / period-start

        period-explicit trigabs)

         trigrel    = date-time "/" date-time *(

                    ; [ISO 8601] complete representation basic format for a period the following are optional,
                    ; of time consisting of a start and end. The start but MUST be NOT occur more than once

                      (";" "VALUE" "=" "DURATION") /
                      (";" trigrelparam) /

                    ; before the end.

        period-start = date-time "/" dur-value
        ; [ISO 8601] complete representation basic format for a period following is optional,
                    ; of time consisting of a start and positive duration of time.

   Example: The period starting at 18:00:00 UTC, on January 1, 1997 and
   ending at 07:00:00 UTC on January 2, 1997 would be:

        19970101T180000Z/19970102T070000Z

   Figure 251

   The period start at 18:00:00 on January 1, 1997 and lasting 5 hours and 30 minutes would be:

        19970101T180000Z/PT5H30M

   No additional content value encoding (i.e., BACKSLASH character
   encoding) is defined for this value type.

13.8.  Time Zone Identifier

   Parameter Name: TZID

   Purpose: To specify the identifier for the time zone definition for a
   time component in MAY occur more than once

                      (";" xparam)
                      ) ":"  dur-value

         trigabs    = 1*(

                    ; the property value.

   Description: The parameter following is REQUIRED,
                    ; but MUST be specified on NOT occur more than once

                      (";" "VALUE" "=" "DATE-TIME") /

                    ; the "DTSTART",
   "DTEND", "DUE", "EXDATE" and "RDATE" properties when either a DATE-
   TIME or TIME value type following is specified optional,
                    ; and when the value is not either
   a UTC or a "floating" time.  Refer MAY occur more than once

                      (";" xparam)

                      ) ":" date-time

   Example: A trigger set 15 minutes prior to the DATE-TIME or TIME value
   type definition for a description start of UTC and "floating time" formats.
   This property parameter specifies a text value which uniquely
   identifies the "VTIMEZONE" calendar component to be used when
   evaluating event or
      to-do.

         TRIGGER:-P15M

      A trigger set 5 minutes after the time portion end of the property. event or to-do.

         TRIGGER;RELATED=END:P5M

      A trigger set to an absolute date/time.

         TRIGGER;VALUE=DATE-TIME:19980101T050000Z

3.8.7.  Change Management Component Properties

   The value of the TZID following properties specify change management information in
   calendar components.

3.8.7.1.  Date/Time Created

   Property Name: CREATED

   Purpose: This property parameter will be equal to specifies the value of date and time that the TZID property
   for calendar
      information was created by the matching time zone definition.  An individual "VTIMEZONE" calendar component MUST be specified for each unique "TZID" parameter
   value specified user agent in the iCalendar object.

   The parameter MUST be specified on properties with a DATE-TIME value
   if the DATE-TIME is not either a UTC or a "floating" time.

   The presence of the SOLIDUS character (US-ASCII decimal 47) as a
   prefix, indicates that this TZID represents a unique ID in a globally
   defined time zone registry (when such registry is defined). calendar
      store.

         Note: This document does not define a naming convention for time zone
   identifiers.  Implementers may want is analogous to use the naming conventions
   defined in existing creation date and time zone specifications such as for a
         file in the public-
   domain Olson database [TZ].  The specification of globally unique
   time zone identifiers is not addressed by file system.

   Value Type: DATE-TIME

   Property Parameters: Non-standard property parameters can be
      specified on this document and is left
   for future study. property.

   Conformance: The TZID property parameter MUST NOT can be applied to DATE-TIME or TIME
   properties whose time values are specified once in UTC. "VEVENT", "VTODO"
      or "VJOURNAL" calendar components.

   Description: The use of local date and time in a DATE-TIME or TIME value without the TZID
   property parameter is to be interpreted as a local time value,
   regardless of the existence of "VTIMEZONE" calendar components in the
   iCalendar object.

   For more information see the sections on the data types DATE-TIME and
   TIME. UTC value.

   Format Definition: This The property parameter is defined by the following notation:

        tzidparam

         created    = "TZID" "=" [tzidprefix] paramtext "CREATED" creaparam ":" date-time CRLF

        tzidprefix

         creaparam  = "/" *(";" xparam)

   Example: The following are examples is an example of this property parameter:

        DTSTART;TZID=US-Eastern:19980119T020000

        DTEND;TZID=US-Eastern:19980119T030000

   Figure 254

13.9.  Recurrence Rule

   Value property:

         CREATED:19960329T133000Z

3.8.7.2.  Date/Time Stamp

   Property Name: RECUR DTSTAMP

   Purpose: This value type is used to identify properties The property indicates the date/time that contain
   a recurrence rule specification.

   Description: If the property permits, multiple "recur" values are
   specified by a COMMA character (US-ASCII decimal 44) separated list
   of values.  The value type is a structured value consisting of a list instance of one or more recurrence grammar parts.  Each rule part is defined
   by a NAME=VALUE pair.  The rule parts are separated from each other
   by
      the SEMICOLON character (US-ASCII decimal 59).  The rule parts are
   not ordered in any particular sequence.  Individual rule parts MUST
   only iCalendar object was created.

   Value Type: DATE-TIME

   Property Parameters: Non-standard property parameters can be
      specified once.

   The FREQ rule part identifies the type of recurrence rule. on this property.

   Conformance: This rule
   part property MUST be specified included in the recurrence rule.  Valid values include
   SECONDLY, to specify repeating events based on an interval of a
   second or more; MINUTELY, to specify repeating events based on an
   interval of a minute or more; HOURLY, to specify repeating events
   based on an interval of an hour or more; DAILY, to specify repeating
   events based on an interval of a day "VEVENT", "VTODO",
      "VJOURNAL" or more; WEEKLY, "VFREEBUSY" calendar components.

   Description: The value MUST be specified in the UTC time format.

      This property is also useful to specify
   repeating events based on an interval protocols such as [I-D.ietf-
      calsify-rfc2447bis] that have inherent latency issues with the
      delivery of a week or more; MONTHLY, to
   specify repeating events based on an interval content.  This property will assist in the proper
      sequencing of a month or more; messages containing iCalendar objects.

      This property is different than the "CREATED" and
   YEARLY, "LAST-MODIFIED"
      properties.  These two properties are used to specify repeating events based on an interval when the
      particular calendar data in the calendar store was created and
      last modified.  This is different than when the iCalendar object
      representation of a year the calendar service information was created or
   more.
      last modified.

   Format Definition: The INTERVAL rule part contains a positive integer representing how
   often property is defined by the recurrence rule repeats. following notation:

         dtstamp    = "DTSTAMP" stmparam ":" date-time CRLF

         stmparam   = *(";" xparam)

   Example:

         DTSTAMP:19971210T080000Z

3.8.7.3.  Last Modified

   Property Name: LAST-MODIFIED

   Purpose: The default value is "1", meaning
   every second for a SECONDLY rule, or every minute for a MINUTELY
   rule, every hour for an HOURLY rule, every day for a DAILY rule,
   every week for a WEEKLY rule, every month for a MONTHLY rule property specifies the date and
   every year for a YEARLY rule.

   The UNTIL rule part defines a date-time value which bounds time that the
   recurrence rule
      information associated with the calendar component was last
      revised in an inclusive manner.  If the value specified by
   UNTIL calendar store.

         Note: This is synchronized with analogous to the specified recurrence, this modification date or
   date-time becomes the last instance of and time for a
         file in the recurrence.  If file system.

   Value Type: DATE-TIME

   Property Parameters: Non-standard property parameters can be
      specified
   as a date-time value, then it on this property.

   Conformance: This property can be specified in the "EVENT", "VTODO",
      "VJOURNAL" or "VTIMEZONE" calendar components.

   Description: The property value MUST be specified in an the UTC time
      format.  If not present, and the COUNT rule part

   Format Definition: The property is also not present, defined by the RRULE is considered to repeat forever. following notation:

         last-mod   = "LAST-MODIFIED" lstparam ":" date-time CRLF

         lstparam   = *(";" xparam)

   Example: The COUNT rule part following is are examples of this property:

                   LAST-MODIFIED:19960817T133000Z

3.8.7.4.  Sequence Number

   Property Name: SEQUENCE

   Purpose: This property defines the revision sequence number of occurrences at which to
   range-bound the recurrence.  The "DTSTART" property value, if
   specified, counts as the first occurrence.

   The BYSECOND rule part specifies a COMMA character (US-ASCII decimal
   44) separated list of seconds within a minute.  Valid values are 0 to
   59.  The BYMINUTE rule part specifies a COMMA character (US-ASCII
   decimal 44) separated list of minutes
      calendar component within an hour.  Valid values
   are 0 to 59.  The BYHOUR rule part specifies a COMMA character (US-
   ASCII decimal 44) separated list of hours sequence of the day.  Valid values
   are 0 to 23. revisions.

   Value Type: integer

   Property Parameters: Non-standard property parameters can be
      specified on this property.

   Conformance: The BYDAY rule part specifies property can be specified in "VEVENT", "VTODO" or
      "VJOURNAL" calendar component.

   Description: When a COMMA character calendar component is created, its sequence
      number is zero (US-ASCII decimal 44)
   separated list of days of the week; MO indicates Monday; TU indicates
   Tuesday; WE indicates Wednesday; TH indicates Thursday; FR indicates
   Friday; SA indicates Saturday; SU indicates Sunday.

   Each BYDAY value can also be preceded 48).  It is monotonically
      incremented by the "Organizer's" CUA each time the "Organizer"
      makes a positive (+n) or negative
   (-n) integer.  If present, this indicates significant revision to the nth occurrence of calendar component.  When the
   specific day within
      "Organizer" makes changes to one of the MONTHLY or YEARLY RRULE.  For example, within
   a MONTHLY rule, +1MO (or simply 1MO) represents following properties, the first Monday
   within
      sequence number MUST be incremented:

         "DTSTART"

         "DTEND"

         "DUE"

         "RDATE"

         "RRULE"

         "EXDATE"

         "EXRULE"
         "STATUS"

      In addition, changes made by the month, whereas -1MO represents "Organizer" to other properties
      can also force the last Monday of sequence number to be incremented.  The
      "Organizer" CUA MUST increment the
   month.  If an integer modifier is not present, sequence number when ever it means all days of
   this type within
      makes changes to properties in the specified frequency.  For example, within a
   MONTHLY rule, MO represents all Mondays within calendar component that the month.

   The BYMONTHDAY rule part specifies a COMMA character (ASCII decimal
   44) separated list
      "Organizer" deems will jeopardize the validity of days the
      participation status of the month.  Valid values are 1 to 31 or
   -31 to -1. "Attendees".  For example, -10 represents changing
      the tenth location of a meeting from one locale to another distant
      locale could effectively impact the last day participation status of the month.
      "Attendees".

      The BYYEARDAY rule part specifies a COMMA character (US-ASCII decimal
   44) separated list of days of the year.  Valid values are 1 "Organizer" includes this property in an iCalendar object that
      it sends to 366 or
   -366 an "Attendee" to -1.  For example, -1 represents specify the last day current version of the year
   (December 31st) and -306 represents
      calendar component.

      The "Attendee" includes this property in an iCalendar object that
      it sends to the 306th "Organizer" to specify the last day version of the
   year (March 1st).

   The BYWEEKNO rule part specifies a COMMA character (US-ASCII decimal
   44) separated list of ordinals specifying weeks of calendar
      component that the year.  Valid
   values are 1 to 53 or -53 to -1.  This corresponds to weeks according
   to week numbering as defined in [ISO 8601].  A week "Attendee" is defined as a
   seven day period, starting on referring to.

      A change to the day of sequence number is not the week defined mechanism that an
      "Organizer" uses to be request a response from the
   week start (see WKST).  Week number one of "Attendees".  The
      "RSVP" parameter on the calendar year "ATTENDEE" property is used by the
   first week which contains at least four (4) days in
      "Organizer" to indicate that calendar
   year.  This rule part is only valid for YEARLY rules.  For example, 3
   represents a response from the third week of "Attendees" is
      requested.

   Format Definition: The property is defined by the year.

   Note: Assuming a Monday week start, week 53 can only occur when
   Thursday following notation:

         seq = "SEQUENCE" seqparam ":" integer CRLF
         ; Default is January 1 or if it "0"

         seqparam   = *(";" xparam)

   Example: The following is an example of this property for a leap year and Wednesday is
   January 1. calendar
      component that was just created by the "Organizer".

         SEQUENCE:0

      The BYMONTH rule part specifies following is an example of this property for a COMMA character (US-ASCII decimal
   44) separated list calendar
      component that has been revised two different times by the
      "Organizer".

         SEQUENCE:2

3.8.8.  Miscellaneous Component Properties

   The following properties specify information about a number of months
   miscellaneous features of the year.  Valid values are 1 to 12.

   The WKST rule part specifies the day on which the workweek starts.
   Valid values are MO, TU, WE, TH, FR, SA and SU. calendar components.

3.8.8.1.  Non-standard Properties

   Property Name: Any property name with a "X-" prefix

   Purpose: This is significant
   when class of property provides a WEEKLY RRULE has an interval greater than 1, framework for defining
      non-standard properties.

   Value Type: TEXT

   Property Parameters: Non-standard and a BYDAY rule
   part is specified. language property parameters
      can be specified on this property.

   Conformance: This is also significant when property can be specified in a YEARLY RRULE
   when a BYWEEKNO rule part is specified.  The default value is MO. any calendar
      component.

   Description: The BYSETPOS rule part specifies MIME Calendaring and Scheduling Content Type
      provides a COMMA character (US-ASCII decimal
   44) separated list of values which corresponds "standard mechanism for doing non-standard things".
      This extension support is provided for implementers to "push the nth occurrence
   within
      envelope" on the set existing version of events the memo.  Extension
      properties are specified by property and/or property parameter
      names that have the rule.  Valid values are 1
   to 366 or -366 to -1. prefix text of "X-" (the two character
      sequence: LATIN CAPITAL LETTER X character followed by the HYPEN-
      MINUS character).  It MUST only be used in conjunction with is recommended that vendors concatenate onto
      this sentinel another BYxxx rule part.  For example "the last work day short prefix text to identify the vendor.
      This will facilitate readability of the
   month" could extensions and minimize
      possible collision of names between different vendors.  User
      agents that support this content type are expected to be represented as:

        RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-1

   Each BYSETPOS value able to
      parse the extension properties and property parameters but can include a positive (+n) or negative (-n)
   integer.  If
      ignore them.

      At present, there is no registration authority for names of
      extension properties and property parameters.  The data type for
      this indicates property is TEXT.  Optionally, the nth occurrence data type can be any of
      the
   specific occurrence within the set of events specified other valid data types.

   Format Definition: The property is defined by the rule.

   If BYxxx rule part values are found which are beyond the available
   scope (ie, BYMONTHDAY=30 in February), they are simply ignored.

   Information, not contained in the rule, necessary to determine following notation:

     x-prop     = x-name *(";" xparam) [";" languageparam] ":" text CRLF
        ; Lines longer than 75 octets should be folded
   Example: The following might be the
   various recurrence instance start time and dates are derived from ABC vendor's extension for an
      audio-clip form of subject property:

     X-ABC-MMSUBJ;X-ABC-MMSUBJTYPE=wave:http://load.noise.org/mysubj.wav

3.8.8.2.  Request Status

   Property Name: REQUEST-STATUS

   Purpose: This property defines the
   Start Time (DTSTART) entry attribute.  For example,
   "FREQ=YEARLY;BYMONTH=1" doesn't specify status code returned for a specific day within the
   month
      scheduling request.

   Value Type: TEXT

   Property Parameters: Non-standard and language property parameters
      can be specified on this property.

   Conformance: The property can be specified in "VEVENT", "VTODO",
      "VJOURNAL" or a time. "VFREEBUSY" calendar component.

   Description: This information would be the same as what property is
   specified for DTSTART.

   BYxxx rule parts modify used to return status code information
      related to the recurrence in some manner.  BYxxx rule
   parts processing of an associated iCalendar object.  The
      data type for this property is TEXT.

      The value consists of a period short return status component, a longer
      return status description component, and optionally a status-
      specific data component.  The components of time which is the same or greater than the
   frequency generally reduce or limit value are
      separated by the number of occurrences SEMICOLON character (US-ASCII decimal 59).

      The short return status is a PERIOD character (US-ASCII decimal
      46) separated 3-tuple of the
   recurrence generated. integers.  For example, "FREQ=DAILY;BYMONTH=1" reduces
   the number "3.1.1".  The
      successive levels of recurrence instances from all days (if BYMONTH tag is
   not present) to all days in January.  BYxxx rule parts integers provide for a period successive level of time less than the frequency generally increase or expand
      status code granularity.

      The following are initial classes for the
   number of occurrences of return status code.
      Individual iCalendar object methods will define specific return
      status codes for these classes.  In addition, other classes for
      the recurrence.  For example,
   "FREQ=YEARLY;BYMONTH=1,2" increases return status code may be defined using the number registration
      process defined later in this memo.

        |==============+===============================================|
        | Short Return | Longer Return Status Description              |
        | Status Code  |                                               |
        |==============+===============================================|
        |    1.xx      | Preliminary success. This class of days within status     |
        |              | of status code indicates that the
   yearly recurrence set from 1 (if BYMONTH tag request has |
        |              | request has been initially processed but that |
        |              | completion is not present) to 2.

   If multiple BYxxx rule parts are specified, then after evaluating the
   specified FREQ and INTERVAL rule parts, pending.                        |
        |==============+===============================================|
        |    2.xx      | Successful. This class of status code         |
        |              | indicates that the BYxxx rule parts are
   applied to request was completed      |
        |              | successfuly. However, the current set exact status code   |
        |              | can indicate that a fallback has been taken.  |
        |==============+===============================================|
        |    3.xx      | Client Error. This class of evaluated occurrences in status code       |
        |              | indicates that the following
   order: BYMONTH, BYWEEKNO, BYYEARDAY, BYMONTHDAY, BYDAY, BYHOUR,
   BYMINUTE, BYSECOND and BYSETPOS; then COUNT and UNTIL are evaluated.

   Here request was not successful.|
        |              | The error is an example of evaluating multiple BYxxx rule parts.

        DTSTART;TZID=US-Eastern:19970105T083000
        RRULE:FREQ=YEARLY;INTERVAL=2;BYMONTH=1;BYDAY=SU;BYHOUR=8,9;
         BYMINUTE=30

   First, the "INTERVAL=2" would be applied to "FREQ=YEARLY" to arrive
   at "every other year".  Then, "BYMONTH=1" would be applied to arrive
   at "every January, every other year".  Then, "BYDAY=SU" would be
   applied to arrive at "every Sunday in January, every other year".
   Then, "BYHOUR=8,9" would be applied to arrive at "every Sunday result of either a syntax or |
        |              | a semantic error in
   January at 8 AM and 9 AM, every other year".  Then, "BYMINUTE=30"
   would the client formatted      |
        |              | request. Request should not be applied to arrive at "every Sunday retried until  |
        |              | the condition in January at 8:30 AM and
   9:30 AM, every other year".  Then, lacking information from RRULE, the second request is derived from DTSTART, to end up in "every Sunday in
   January at 8:30:00 AM and 9:30:00 AM, every other year".  Similarly,
   if corrected.    |
        |==============+===============================================|
        |    4.xx      | Scheduling Error. This class of status code   |
        |              | indicates that the BYMINUTE, BYHOUR, BYDAY, BYMONTHDAY or BYMONTH rule part were
   missing, request was not successful.|
        |              | Some sort of error occurred within the appropriate minute, hour, day or month would have been
   retrieved from        |
        |              | calendaring and scheduling service, not       |
        |              | directly related to the "DTSTART" property.

   No additional content value encoding (i.e., BACKSLASH character
   encoding) is defined for this value type.

   Formal request itself.       |
        |==============+===============================================|

   Format Definition: The value type property is defined by the following notation:

        recur

         rstatus    = "REQUEST-STATUS" rstatparam ":"
                      statcode ";" statdesc [";" extdata]

         rstatparam = "FREQ"=freq *(

                    ; either UNTIL or COUNT may appear in a 'recur', the following is optional,
                    ; but UNTIL and COUNT MUST NOT occur in the same 'recur'

              ( ";" "UNTIL" "=" enddate ) /
              ( ";" "COUNT" "=" 1*DIGIT ) more than once

                    (";" languageparm) /

                    ; the rest of these keywords are following is optional,
                    ; but MUST NOT and MAY occur more than once

              ( ";" "INTERVAL" "=" 1*DIGIT )          /
              ( ";" "BYSECOND" "=" byseclist )        /
              ( ";" "BYMINUTE" "=" byminlist )        /
              ( ";" "BYHOUR" "=" byhrlist )           /
              ( ";" "BYDAY" "=" bywdaylist )          /
              ( ";" "BYMONTHDAY" "=" bymodaylist )    /
              ( ";" "BYYEARDAY" "=" byyrdaylist )     /
              ( ";" "BYWEEKNO" "=" bywknolist )       /
              ( ";" "BYMONTH" "=" bymolist )          /
              ( ";" "BYSETPOS" "=" bysplist )         /
              ( ";" "WKST" "=" weekday )              /
              ( ";" x-name "=" text )
               )

        freq = "SECONDLY" / "MINUTELY" / "HOURLY" / "DAILY"
                   / "WEEKLY" / "MONTHLY" / "YEARLY"

        enddate    = date
        enddate    =/ date-time            ;An UTC value
        byseclist  = seconds / ( seconds *("," seconds) )

        seconds    = 1DIGIT / 2DIGIT       ;0 to 59

        byminlist  = minutes / ( minutes *("," minutes) )

        minutes    = 1DIGIT / 2DIGIT       ;0 to 59

        byhrlist   = hour / ( hour *("," hour) )

        hour       = 1DIGIT / 2DIGIT       ;0 to 23

        bywdaylist = weekdaynum / ( weekdaynum *("," weekdaynum) )

        weekdaynum = [([plus] ordwk / minus ordwk)] weekday

        plus       = "+"

        minus      = "-"

        ordwk      = 1DIGIT / 2DIGIT       ;1 to 53

        weekday    = "SU" / "MO" / "TU" / "WE" / "TH" / "FR" / "SA"
        ;Corresponding to SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY,
        ;FRIDAY, SATURDAY and SUNDAY days of the week.

        bymodaylist = monthdaynum / ( monthdaynum *("," monthdaynum) )

        monthdaynum = ([plus] ordmoday) / (minus ordmoday)

        ordmoday   = 1DIGIT / 2DIGIT       ;1 to 31

        byyrdaylist = yeardaynum / ( yeardaynum *("," yeardaynum) )

        yeardaynum = ([plus] ordyrday) / (minus ordyrday)

        ordyrday   = 1DIGIT / 2DIGIT / 3DIGIT      ;1 to 366

        bywknolist = weeknum / ( weeknum *("," weeknum) )

        weeknum    = ([plus] ordwk) / (minus ordwk)

        bymolist   = monthnum / ( monthnum *("," monthnum)

                    (";" xparam)

                    )

        monthnum

         statcode   = 1DIGIT / 2DIGIT       ;1 to 12

        bysplist 1*DIGIT *("." 1*DIGIT)
         ;Hierarchical, numeric return status code

         statdesc   = setposday / ( setposday *("," setposday) )
        setposday text
         ;Textual status description

         extdata    = yeardaynum

   Example: The following is a rule which specifies 10 meetings which
   occur every other day:

        FREQ=DAILY;COUNT=10;INTERVAL=2

   Figure 258

   There are other examples specified in the "RRULE" specification.

13.10.  Float

   Value Name: FLOAT

   Purpose: This value type is used to identify properties that contain
   a real number value.

   Description: If text
         ;Textual exception data. For example, the offending property permits, multiple "float" values
         ;name and value or complete property line.

   Example: The following are
   specified by a COMMA character (US-ASCII decimal 44) separated list some possible examples of values.

   No additional content this property.

      The COMMA and SEMICOLON separator characters in the property value encoding (i.e.,
      are BACKSLASH character
   encoding) escaped because they appear in a text
      value.

     REQUEST-STATUS:2.0;Success

     REQUEST-STATUS:3.1;Invalid property value;DTSTART:96-Apr-01

     REQUEST-STATUS:2.8; Success\, repeating event ignored. Scheduled
      as a single event.;RRULE:FREQ=WEEKLY\;INTERVAL=2

     REQUEST-STATUS:4.1;Event conflict. Date/time is defined for busy.

     REQUEST-STATUS:3.7;Invalid calendar user;ATTENDEE:
      MAILTO:jsmith@host.com

4.  iCalendar Object Examples

   The following examples are provided as an informational source of
   illustrative iCalendar objects consistent with this value content type.

   Formal Definition:

   The value type is defined by the following
   notation:

        float      = (["+"] / "-") 1*DIGIT ["." 1*DIGIT]

   Example:

        1000000.0000001
        1.333
        -3.14

   Figure 260

13.11.  Integer

   Value Name:INTEGER

   Purpose: This value type is used to identify properties example specifies a three-day conference that contain begins at
   8:00 AM EDT, September 18, 1996 and end at 6:00 PM EDT, September 20,
   1996.

        BEGIN:VCALENDAR
        PRODID:-//xyz Corp//NONSGML PDA Calendar Version 1.0//EN
        VERSION:2.0
        BEGIN:VEVENT
        DTSTAMP:19960704T120000Z
        UID:uid1@host.com
        ORGANIZER:MAILTO:jsmith@host.com
        DTSTART:19960918T143000Z
        DTEND:19960920T220000Z
        STATUS:CONFIRMED
        CATEGORIES:CONFERENCE
        SUMMARY:Networld+Interop Conference
        DESCRIPTION:Networld+Interop Conference
          and Exhibit\nAtlanta World Congress Center\n
         Atlanta, Georgia
        END:VEVENT
        END:VCALENDAR

   The following example specifies a signed integer value.

   Description: If group scheduled meeting that begin
   at 8:30 AM EST on March 12, 1998 and end at 9:30 AM EST on March 12,
   1998.  The "Organizer" has scheduled the property permits, multiple "integer" values are
   specified by meeting with one or more
   calendar users in a COMMA character (US-ASCII decimal 44) separated list group.  A time zone specification for Eastern
   United States has been specified.

        BEGIN:VCALENDAR
        PRODID:-//RDU Software//NONSGML HandCal//EN
        VERSION:2.0
        BEGIN:VTIMEZONE
        TZID:US-Eastern
        BEGIN:STANDARD
        DTSTART:19981025T020000
        RDATE:19981025T020000
        TZOFFSETFROM:-0400
        TZOFFSETTO:-0500
        TZNAME:EST
        END:STANDARD
        BEGIN:DAYLIGHT
        DTSTART:19990404T020000
        RDATE:19990404T020000
        TZOFFSETFROM:-0500
        TZOFFSETTO:-0400
        TZNAME:EDT
        END:DAYLIGHT
        END:VTIMEZONE
        BEGIN:VEVENT
        DTSTAMP:19980309T231000Z
        UID:guid-1.host1.com
        ORGANIZER;ROLE=CHAIR:MAILTO:mrbig@host.com
        ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT;CUTYPE=GROUP:
         MAILTO:employee-A@host.com
        DESCRIPTION:Project XYZ Review Meeting
        CATEGORIES:MEETING
        CLASS:PUBLIC
        CREATED:19980309T130000Z
        SUMMARY:XYZ Project Review
        DTSTART;TZID=US-Eastern:19980312T083000
        DTEND;TZID=US-Eastern:19980312T093000
        LOCATION:1CP Conference Room 4350
        END:VEVENT
        END:VCALENDAR

   The following is an example of values. an iCalendar object passed in a MIME
   message with a single body part consisting of a "text/calendar"
   Content Type.

        TO:jsmith@host1.com
        FROM:jdoe@host1.com
        MIME-VERSION:1.0
        MESSAGE-ID:<id3@host1.com>
        CONTENT-TYPE:text/calendar

        BEGIN:VCALENDAR
        METHOD:xyz
        VERSION:2.0
        PRODID:-//ABC Corporation//NONSGML My Product//EN
        BEGIN:VEVENT
        DTSTAMP:19970324T120000Z
        SEQUENCE:0
        UID:uid3@host1.com
        ORGANIZER:MAILTO:jdoe@host1.com
        ATTENDEE;RSVP=TRUE:MAILTO:jsmith@host1.com
        DTSTART:19970324T123000Z
        DTEND:19970324T210000Z
        CATEGORIES:MEETING,PROJECT
        CLASS:PUBLIC
        SUMMARY:Calendaring Interoperability Planning Meeting
        DESCRIPTION:Discuss how we can test c&s interoperability\n
         using iCalendar and other IETF standards.
        LOCATION:LDB Lobby
        ATTACH;FMTTYPE=application/postscript:ftp://xyzCorp.com/pub/
         conf/bkgrnd.ps
        END:VEVENT
        END:VCALENDAR

   The valid range for "integer" following is -2147483648 an example of a to-do due on April 15, 1998.  An
   audio alarm has been specified to
   2147483647.  If remind the sign is not specified, then calendar user at noon,
   the value day before the to-do is assumed expected to be completed and repeat
   hourly, four additional times.  The to-do definition has been
   modified twice since it was initially created.

        BEGIN:VCALENDAR
        VERSION:2.0
        PRODID:-//ABC Corporation//NONSGML My Product//EN
        BEGIN:VTODO
        DTSTAMP:19980130T134500Z
        SEQUENCE:2
        UID:uid4@host1.com
        ORGANIZER:MAILTO:unclesam@us.gov
        ATTENDEE;PARTSTAT=ACCEPTED:MAILTO:jqpublic@host.com
        DUE:19980415T235959
        STATUS:NEEDS-ACTION
        SUMMARY:Submit Income Taxes
        BEGIN:VALARM
        ACTION:AUDIO
        TRIGGER:19980403T120000
        ATTACH;FMTTYPE=audio/basic:http://host.com/pub/audio-
         files/ssbanner.aud
        REPEAT:4
        DURATION:PT1H
        END:VALARM
        END:VTODO
        END:VCALENDAR

   The following is an example of a journal entry.

        BEGIN:VCALENDAR
        VERSION:2.0
        PRODID:-//ABC Corporation//NONSGML My Product//EN
        BEGIN:VJOURNAL
        DTSTAMP:19970324T120000Z
        UID:uid5@host1.com
        ORGANIZER:MAILTO:jsmith@host.com
        STATUS:DRAFT
        CLASS:PUBLIC
        CATEGORY:Project Report, XYZ, Weekly Meeting
        DESCRIPTION:Project xyz Review Meeting Minutes\n
         Agenda\n1. Review of project version 1.0 requirements.\n2.
        Definition
         of project processes.\n3. Review of project schedule.\n
         Participants: John Smith, Jane Doe, Jim Dandy\n-It was
          decided that the requirements need to be signed off by
          product marketing.\n-Project processes were accepted.\n
         -Project schedule needs to account for scheduled holidays
          and employee vacation time. Check with HR for specific
          dates.\n-New schedule will be positive.

   No additional content value encoding (i.e., BACKSLASH character
   encoding) distributed by Friday.\n-
         Next weeks meeting is defined for this value type.

   Formal Definition: cancelled. No meeting until 3/23.
        END:VJOURNAL
        END:VCALENDAR
   The value type is defined by the following
   notation:

        integer    = (["+"] / "-") 1*DIGIT

   Example:

        1234567890
        -1234567890
        +1234567890
        432109876

   Figure 262

13.12.  Text

   Value Name: TEXT

   Purpose This value type is used to identify values that contain human
   readable text.

   Description: If the property permits, multiple "text" values are
   specified by a COMMA character (US-ASCII decimal 44) separated list an example of values. published busy time information.  The language in which the text is represented can be controlled by
   the "LANGUAGE" property parameter.

   An intentional formatted text line break MUST only
   iCalendar object might be included placed in a
   "TEXT" property value by representing the line break with the
   character sequence of BACKSLASH (US-ASCII decimal 92), network resource
   www.host.com/calendar/busytime/jsmith.ifb.

        BEGIN:VCALENDAR
        VERSION:2.0
        PRODID:-//RDU Software//NONSGML HandCal//EN
        BEGIN:VFREEBUSY
        ORGANIZER:MAILTO:jsmith@host.com
        DTSTART:19980313T141711Z
        DTEND:19980410T141711Z
        FREEBUSY:19980314T233000Z/19980315T003000Z
        FREEBUSY:19980316T153000Z/19980316T163000Z
        FREEBUSY:19980318T030000Z/19980318T040000Z
        URL:http://www.host.com/calendar/busytime/jsmith.ifb
        END:VFREEBUSY
        END:VCALENDAR

5.  Recommended Practices

   These recommended practices should be followed by a
   LATIN SMALL LETTER N (US-ASCII decimal 110) or a LATIN CAPITAL LETTER
   N (US-ASCII decimal 78), that is "\n" or "\N".

   The "TEXT" property values may also contain special characters that
   are used to signify delimiters, such as a COMMA character for lists
   of values or a SEMICOLON character for structured values.  In in order to support the inclusion assure
   consistent handling of these special characters in "TEXT"
   property values, they MUST the following cases for an iCalendar object.

   1.   Content lines longer than 75 octets SHOULD be escaped with a BACKSLASH character. folded.

   2.   A
   BACKSLASH character (US-ASCII decimal 92) in a "TEXT" property value
   MUST be escaped calendar entry with another BACKSLASH character.  A COMMA character
   in a "TEXT" "DTSTART" property value MUST be escaped with a BACKSLASH character
   (US-ASCII decimal 92).  A SEMICOLON character in a "TEXT" but no "DTEND"
        property
   value MUST be escaped does not take up any time.  It is intended to represent
        an event that is associated with a BACKSLASH character (US-ASCII decimal
   92).  However, a COLON character in a "TEXT" property value SHALL given calendar date and time
        of day, such as an anniversary.  Since the event does not take
        up any time, it MUST NOT be escaped with a BACKSLASH character.

   Formal Definition: The character sets supported by this revision of
   iCalendar are UTF-8 and US ASCII thereof.  The applicability used to other
   character sets is record busy time no matter
        what the value for future work.  The the "TRANSP" property.

   3.   When the "DTSTART" and "DTEND", for "VEVENT", "VJOURNAL" and
        "VFREEBUSY" calendar components, and "DTSTART" and "DUE", for
        "VTODO" calendar components, have the same value data type is defined
        (e.g., DATE-TIME), they SHOULD specify values in the same time
        format (e.g., UTC time format).

   4.   When the combination of the "RRULE" and "RDATE" properties on an
        iCalendar object produces multiple instances having the same
        start date/time, they should be collapsed to, and considered as,
        a single instance.

   5.   When a calendar user receives multiple requests for the same
        calendar component (e.g., REQUEST for a "VEVENT" calendar
        component) as a result of being on multiple mailing lists
        specified by "ATTENDEE" properties in the
   following notation.

        text       = *(TSAFE-CHAR / ":" / DQUOTE / ESCAPED-CHAR)
        ; Folded according request, they SHOULD
        respond to description above

        ESCAPED-CHAR = "\\" / "\;" / "\," / "\N" / "\n")
           ; \\ encodes \, \N or \n encodes newline
           ; \; encodes ;, \, encodes ,

        TSAFE-CHAR = %x20-21 / %x23-2B / %x2D-39 / %x3C-5B
                     %x5D-7E / NON-US-ASCII
           ; Any character except CTLs not needed by the current
           ; character set, DQUOTE, ";", ":", "\", ","

   Note: Certain other character sets may require modification only one of the
   above definitions, but this is beyond requests.  The calendar user SHOULD
        also specify (using the scope "MEMBER" parameter of this document.

   Example: A multiple line value of:

        Project XYZ Final Review
        Conference Room - 3B
        Come Prepared.

      would be represented as:

        Project XYZ Final Review\nConference Room - 3B\nCome Prepared.

   Figure 264

13.13.  Time

   Value Name: TIME

   Purpose: This the "ATTENDEE"
        property) which mailing list they are a member of.

   6.   An implementation can truncate a "SUMMARY" property value type is used to identify values that contain a
   time of day.

   Description: 255
        characters.

   7.   If seconds of the property permits, multiple "time" values minute are
   specified not supported by an implementation,
        then a COMMA character (US-ASCII decimal 44) separated list
   of values.  No additional content value encoding (i.e., BACKSLASH
   character encoding) is defined of "00" SHOULD be specified for this the seconds
        component in a time value.

   8.   If the value type.

   The "TIME" data type is used to identify parameter (VALUE=) contains an unknown value
        type, it SHOULD be treated as TEXT.

   9.   TZURL values that contain SHOULD NOT be specified as a time
   of day.  The format FILE URI type.  This
        URI form can be useful within an organization, but is based on
        problematic in the [ISO 8601] complete
   representation, basic format Internet.

   10.  Some possible English values for a time CATEGORIES property include
        "ANNIVERSARY", "APPOINTMENT", "BUSINESS", "EDUCATION",
        "HOLIDAY", "MEETING", "MISCELLANEOUS", "NON-WORKING HOURS", "NOT
        IN OFFICE", "PERSONAL", "PHONE CALL", "SICK DAY", "SPECIAL
        OCCASION", "TRAVEL", "VACATION".  Categories can be specified in
        any registered language.

   11.  Some possible English values for RESOURCES property include
        "CATERING", "CHAIRS", "COMPUTER PROJECTOR", "EASEL", "OVERHEAD
        PROJECTOR", "SPEAKER PHONE", "TABLE", "TV", "VCR", "VIDEO
        PHONE", "VEHICLE".  Resources can be specified in any registered
        language.

6.  Registration of day.  The text format
   consists Content Type Elements

   This section provides the process for registration of MIME
   Calendaring and Scheduling Content Type iCalendar object methods and
   new or modified properties.

6.1.  Registration of New and Modified iCalendar Object Methods

   New MIME Calendaring and Scheduling Content Type iCalendar object
   methods are registered by the publication of an IETF Request for
   Comments (RFC).  Changes to an iCalendar object method are registered
   by the publication of a two-digit 24-hour revision of the day (i.e., values 0-23), two-
   digit minute in RFC defining the hour (i.e., method.

6.2.  Registration of New Properties

   This section defines procedures by which new properties or enumerated
   property values 0-59), for the MIME Calendaring and Scheduling Content Type
   can be registered with the IANA.  Non-IANA properties can be used by
   bilateral agreement, provided the associated properties names follow
   the "X-" convention.

   The procedures defined here are designed to allow public comment and two-digit seconds
   in the minute (i.e., values 0-60).  The seconds value
   review of 60 MUST new properties, while posing only a small impediment to be used to account for "leap" seconds.  Fractions the
   definition of new properties.

   Registration of a second are
   not supported new property is accomplished by this format.

   In parallel to the "DATE-TIME" definition above, following
   steps.

6.2.1.  Define the "TIME" data type
   expresses time values in three forms: property

   A property is defined by completing the following template.

           To: ietf-calendar@imc.org

           Subject: Registration of text/calendar MIME property XXX

           Property name:

           Property purpose:

           Property value type(s):

           Property parameter (s):

           Conformance:

           Description:

           Format definition:

           Examples:

   The form meaning of time with UTC offset MUST NOT be used.  For example, each field in the
   following template is NOT VALID for a time value:

        230000-0800        ;Invalid time format

      FORM #1 LOCAL TIME as follows.

   Property name: The local time form is simply a time value that does not contain name of the
   UTC designator nor does property, as it reference a time zone.  For example, 11:00
   PM:

        230000

   Time values of this type are said to be "floating" and are not bound
   to any time zone will appear in particular.  They are used to represent the same
   hour, minute, and second value regardless
      body of which time zone is
   currently being observed.  For example, an event can be defined that
   indicates that an individual will be busy from 11:00 AM text/calendar MIME Content-Type "property: value" line
      to 1:00 PM
   every day, no matter which time zone the person is in.  In these
   cases, a local time can be specified. left of the colon ":".

   Property purpose: The recipient purpose of an iCalendar
   object with a the property value consisting of (e.g., to indicate a local time, without any
   relative time zone information, SHOULD interpret
      delegate for the event or to-do, etc.).  Give a short but clear
      description.

   Property value as being
   fixed to whatever time zone type (s): Any of the ATTENDEE is in at any given moment.
   This means that two ATTENDEEs may participate in valid value types for the same event at
   different UTC times; floating time SHOULD only be used where that is
   reasonable behavior.

   In most cases, a fixed time is desired.  To properly communicate a
   fixed time in a
      property value, either UTC time or local time with
   time zone reference MUST value needs to be specified.  The use of local time in default value type also
      needs to be specified.  If a TIME new value without the TZID property
   parameter type is specified, it needs
      to be interpreted as a local time value, regardless declared in this section.

   Property parameter (s): Any of the existence of "VTIMEZONE" valid property parameters for the
      property needs to be specified.

   Conformance: The calendar components that the property can appear in
      needs to be specified.

   Description: Any special notes about the iCalendar
   object.

      FORM #2: UTC TIME

   UTC time, or absolute time, property, how it is identified by a LATIN CAPITAL LETTER Z
   suffix character (US-ASCII decimal 90), to be
      used, etc.

   Format definition: The ABNF for the UTC designator, appended property definition needs to be
      specified.

   Examples: One or more examples of instances of the property needs to
      be specified.

6.2.2.  Post the time value.  For example, Property definition

   The property description MUST be posted to the new property
   discussion list, ietf-calendar@imc.org.

6.2.3.  Allow a comment period

   Discussion on the following represents 07:00 AM
   UTC:

        070000Z

   The TZID new property parameter MUST NOT be applied to TIME properties
   whose time values are specified in UTC.

      FORM #3: LOCAL TIME AND TIME ZONE REFERENCE

   The local time with reference allowed to time zone information form is
   identified by take place on the use
   list for a minimum of two weeks.  Consensus MUST be reached on the TZID
   property parameter before proceeding to reference the
   appropriate time zone definition.  TZID is discussed in detail in next step.

6.2.4.  Submit the
   section on Time Zone.

   Formal Definition: The data type is defined by property for approval

   Once the following
   notation:

        time = time-hour time-minute time-second [time-utc]

        time-hour          = 2DIGIT        ;00-23
        time-minute        = 2DIGIT        ;00-59
        time-second        = 2DIGIT        ;00-60
        ;The "60" value two-week comment period has elapsed, and the proposer is used
   convinced consensus has been reached on the property, the
   registration application should be submitted to account the Method Reviewer
   for "leap" seconds.

        time-utc   = "Z"

   Example: approval.  The following represents 8:30 AM in New York in Winter, five
   hours behind UTC, in each of the three formats using the "X-
   TIMEOFDAY" non-standard property:

        X-TIMEOFDAY:083000

        X-TIMEOFDAY:133000Z

        X-TIMEOFDAY;TZID=US-Eastern:083000

   Figure 272

13.14.  URI

   Value Name: URI

   Purpose: This value type Method Reviewer is used to identify values that contain a
   uniform resource identifier (URI) type of reference appointed to the Application
   Area Directors and can either accept or reject the property
   value.

   Description: This data type might
   registration.  An accepted registration should be used passed on by the
   Method Reviewer to reference binary
   information, the IANA for values that are large, or otherwise undesirable to
   include directly inclusion in the iCalendar object.

   The URI value formats in RFC 1738, RFC 2111 and any other IETF
   registered value format can be specified.

   Any official IANA registered URI format method
   registry.  The registration can be used.  These include, but are rejected for any of the following
   reasons. 1) Insufficient comment period; 2) Consensus not limited to, those defined in RFC 1738 and RFC 2111.

   When reached; 3)
   Technical deficiencies raised on the list or elsewhere have not been
   addressed.  The Method Reviewer's decision to reject a property parameter value is a URI value type, can
   be appealed by the URI MUST proposer to the IESG, or the objections raised can
   be
   specified as a quoted-string value.

   No additional content value encoding (i.e., BACKSLASH character
   encoding) is defined for this value type.

   Formal Definition: The data type is defined addressed by the following
   notation:

        uri        = <As defined proposer and the property resubmitted.

6.3.  Property Change Control

   Existing properties can be changed using the same process by any IETF RFC>

   Example: The following is which
   they were registered.

   1.  Define the change

   2.  Post the change

   3.  Allow a URI comment period

   4.  Submit the property for approval

   Note that the original author or any other interested party can
   propose a network file:

        http://host1.com/my-report.txt

   Figure 274

13.15.  UTC Offset

   Value Name: UTC-OFFSET

   Purpose: This value type is used change to identify properties that contain an offset from UTC to local time.

   Description: The PLUS SIGN character MUST be specified for positive
   UTC offsets (i.e., ahead of UTC).  The MINUS SIGN character MUST be
   specified for negative UTC offsets (i.e., behind of UTC).  The value
   of "-0000" and "-000000" existing property, but that such changes
   should only be proposed when there are not allowed. serious omissions or errors in
   the published memo.  The time-second, if
   present, may not be 60; Method Reviewer can object to a change if absent, it defaults to zero.

   No additional content value encoding (i.e., BACKSLASH character
   encoding)
   is defined for this value type.

   Formal Definition: The data type not backward compatible, but is defined by not required to do so.

   Property definitions can never be deleted from the following
   notation:

        utc-offset = time-numzone  ;As defined above in time data type

        time-numzone       = ("+" / "-") time-hour time-minute [time-
        second]

   Example: The following UTC offsets IANA registry, but
   properties which are given for standard time for
   New York (five hours behind UTC) and Geneva (one hour ahead of UTC):

        -0500

        +0100

   Figure 276

14. no longer believed to be useful can be declared
   OBSOLETE by a change to their "intended use" field.

7.  Internationalization Considerations

8.  Security Considerations

   SPOOFING - -

   SPOOFING: In this memo, the "Organizer" is the only person authorized
      to make changes to an existing "VEVENT", "VTODO", "VJOURNAL"
      calendar component and redistribute the updates to the
      "Attendees".  An iCalendar object that maliciously changes or
      cancels an existing "VEVENT", "VTODO" or "VJOURNAL" or "VFREEBUSY"
      calendar component might be constructed by someone other than the
      "Organizer" and sent to the "Attendees".  In addition in this
      memo, other than the "Organizer", an "Attendee" of a "VEVENT",
      "VTODO", "VJOURNAL" calendar component is the only other person
      authorized to update any parameter associated with their
      "ATTENDEE" property and send it to the "Organizer".  An iCalendar
      object that maliciously changes the "ATTENDEE" parameters can be
      constructed by someone other than the real "Attendee" and sent to
      the "Organizer".

   PROCEDURAL ALARMS - - ALARMS: An iCalendar object can be created that contains a
      "VEVENT" and "VTODO" calendar component with "VALARM" calendar
      components.  The "VALARM" calendar component can be of type
      PROCEDURE and can have an attachment containing some sort of
      executable program.  Implementations that incorporate these types
      of alarms are subject to any virus or malicious attack that might
      occur as a result of executing the attachment.

   ATTACHMENTS - -

   ATTACHMENTS: An iCalendar object can include references to Uniform
      Resource Locators that can be programmed resources.

      Implementers and users of this memo should be aware of the network
      security implications of accepting and parsing such information.
      In addition, the security considerations observed by
      implementations of electronic mail systems should be followed for
      this memo.

15.

9.  IANA MIME Media Type Registration

   [[Comment.6: We will need to check out the new Consideration

9.1.  Media Type Registration Procedures defined in draft-freed-media-type-reg-05.txt.
   --bdesruisseaux]] Information

   The following text Calendaring and Scheduling Core Object Specification is intended to register this memo
   for use as a MIME content type.  However, the implementation of the
   memo is in no way limited solely as a MIME content type "text/calendar". type.

   To: ietf-types@iana.org
   Subject: Registration of MIME content type text/calendar.

   MIME media type text/calendar

   Type name: text

   MIME subtype

   Subtype name: calendar

   Required parameters: none

   Optional parameters: charset, method, component and optinfo

      The "charset" parameter is defined in MIME Media Types [5]. [RFC2046] for other body
      parts.  It is used to identify the default character set used
      within the body part.

      The "method" parameter contains is used to convey the iCalendar object method.
      method or transaction semantics for the calendaring and scheduling
      information.  It also is an identifier for the restricted set of
      properties and values that the iCalendar object consists of.  The
      parameter is to be used as a guide for applications interpreting
      the information contained within the body part.  It SHOULD NOT be
      used to exclude or require particular pieces of information unless
      the identified method definition specifically calls for this
      behavior.  Unless specifically forbidden by a particular method
      definition, a text/calendar content type can contain any set of
      properties permitted by the Calendaring and Scheduling Core Object
      Specification.  The "method" parameter MUST be the same value as
      that specified in the "METHOD" component property in the iCalendar
      object.  If one is present, the other MUST also be present.

      The value for the "method" parameter is defined as follows:

     method  = 1*(ALPHA / DIGIT / "-")
     ; IANA registered iCalendar object method

      The "component" parameter conveys the type of iCalendar calendar
      component within the body part.  If the iCalendar object contains
      more than one calendar component type, then multiple component
      parameters MUST be specified.  [[Comment.7: I believe this is
      ambiguous about whether the 'component' parameter is always
      required. --Lisa D]]

      The value for the "component" parameter is defined as follows:

     component = ("VEVENT" "VEVENT"
               / "VTODO"
               / "VJOURNAL"
               / "VFREEBUSY"
               / "VTIMEZONE"
               / x-name
               / iana-token) iana-token

      The "optinfo" parameter conveys optional information about the
      iCalendar object within the body part.  This parameter can only
      specify semantics already specified by the iCalendar object and
      that can be otherwise determined by parsing the body part.  In
      addition, the optional information specified by this parameter
      MUST be consistent with that information specified by the
      iCalendar object.  For example, it can be used to convey the
      "Attendee" response status to a meeting request.  The parameter
      value consists of a string value.

      The "optinfo" parameter can be specified multiple times.

      This parameter MAY only specify semantics already specified by the
      iCalendar object and that can be otherwise determined by parsing
      the body part.  [[Comment.8: I believe that 'optinfo' is
      underspecified and interoperability probably cannot even be
      tested.  If nobody uses it we need to delete this parameter.
      --Lisa D]]

      The value for the "optinfo" parameter is defined as follows:

     optinfo    = infovalue / qinfovalue

     infovalue  = iana-token / x-name

     qinfovalue = DQUOTE (infovalue) DQUOTE
   Encoding Considerations: considerations: This MIME content media type can contain 8bit characters,
      so the use of quoted-printable or BASE64 base64 MIME content-
      transfer-encodings Content-Transfer-
      Encodings might be necessary when iCalendar objects are
      transferred across protocols restricted to the 7bit repertoire.
      Note that a text valued property in the content entity can also
      have content encoding of special characters using a BACKSLASH
      character (US-ASCII decimal 92) escapement technique.  This means
      that content values can end up encoded twice.

   Security Considerations: considerations: See the Security Considerations section of
      this document. Section 8.

   Interoperability Considerations: considerations: This MIME content media type is intended to
      define a common format for conveying calendaring and scheduling
      information between different systems.  It is heavily based on the
      earlier [VCAL] industry specification.

   Published Specification: specification: This document. specification.

   Applications Which Use This Media Type: which use this media type: This media type is designed
      for widespread use by Internet calendaring and scheduling
      applications.  In addition, applications in the workflow and
      document management area might find this media type content-type applicable.
      The [ITIP] iTIP [I-D.ietf-calsify-2446bis], iMIP [I-D.ietf-calsify-
      rfc2447bis] and [IMIP] CalDAV [I-D.dusseault-caldav] Internet protocols
      directly use this type.
      [[Comment.9: Consider adding CalDAV. --Lisa D]] media type also.

   Additional information:

      Magic Numbers:  None number(s): None.

      File Extensions: extension(s): The file extension of "ics" is to be used to
         designate a file containing (an arbitrary set of) calendaring
         and scheduling information consistent with this MIME content
         type.

         The file extension of "ifb" is to be used to designate a file
         containing free or busy time information consistent with this
         MIME content type.

      Macintosh file type codes: code(s): The file type code of "iCal" is to be
         used in Apple MacIntosh operating system environments to
         designate a file containing calendaring and scheduling
         information consistent with this MIME media type.

         The file type code of "iFBf" is to be used in Apple MacIntosh
         operating system environments to designate a file containing
         free or busy time information consistent with this MIME media
         type.

   Contact

   Person & email address to contact for Further Information: further information: TBD

   Intended Usage: usage: COMMON

16.  Acknowledgements

   Restrictions on usage: There are no restrictions on where this media
      type can be used.

   Author: TBD

   Change controller: IETF

10.  Acknowledgments

   The editors editor of this document wish to thank Frank Dawson and Stenerson
   Derik, the original author of this document. RFC2445.

   The editors editor would also like to thank the Calendaring and Scheduling
   Consortium for advice with this specification, and for organizing
   interoperability testing events to help refine it.

17.

11.  References

11.1.  Normative References

   [1]

   [I-D.ietf-calsify-2446bis]
              Daboo, C., "iCalendar Transport-Independent
              Interoperability Protocol (iTIP)",
              draft-ietf-calsify-2446bis-01 (work in progress),
              March 2006.

   [I-D.ietf-calsify-rfc2447bis]
              Melnikov, A., "iCalendar Message-Based Interoperability
              Protocol(iMIP)", draft-ietf-calsify-rfc2447bis-02 (work in
              progress), June 2006.

   [ISO.8601.1988]
              International Organization for Standardization, "Data
              elements and interchange formats - Information interchange
              - Representation of dates and times",
              <http://www.w3.org/TR/NOTE-datetime>.

   [ISO.9070.1991]
              International Organization for Standardization,
              "Information Technology_SGML Support Facilities --
              Registration Procedures for Public Text Owner Identifiers,
              Second Edition", April 1991, <http://www.ietf.org/
              proceedings/98dec/I-D/draft-ietf-calsch-icalfpi-00.txt>.

   [RFC0822]  Crocker, D., "Standard for the format of ARPA Internet
              text messages", STD 11, RFC 822, August 1982.

   [2]

   [RFC1738]  Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
              Resource Locators (URL)", RFC 1738, December 1994.

   [3]

   [RFC1766]  Alvestrand, H., "Tags for the Identification of
              Languages", RFC 1766, March 1995.

   [4]

   [RFC2045]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part One: Format of Internet Message
              Bodies", RFC 2045, November 1996.

   [5]

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              November 1996.

   [6]   Freed, N., Klensin, J., and J. Postel, "Multipurpose Internet
         Mail Extensions (MIME) Part Four: Registration Procedures",
         BCP 13, RFC 2048, November 1996.

   [7]

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [8]

   [RFC2234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 2234, November 1997.

   [9]

   [RFC2279]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", RFC 2279, January 1998.

   [10]

   [RFC2425]  Howes, T., Smith, M., and F. Dawson, "A MIME Content-Type
              for Directory Information", RFC 2425, September 1998.

   [RFC2426]  Dawson, F. and T. Howes, "vCard MIME Directory Profile",
              RFC 2426, September 1998.

   [11]  Dawson, F. and Stenerson, D., "Internet Calendaring and
         Scheduling Core Object Specification (iCalendar)", RFC 2445,
         November 1998.

   [12]  Silverberg, S., Mansour, S., Dawson, F., and R. Hopson,
         "iCalendar Transport-Independent Interoperability Protocol
         (iTIP) Scheduling Events, BusyTime, To-dos and Journal
         Entries", RFC 2446, November 1998.

   [13]  International Organization for Standardization, "Data elements
         and interchange formats- Information interchange-
         -Representation of dates and times",
         <http://www.w3.org/TR/NOTE-datetime>.

   [14]  International Organization for Standardization, "Information
         Technology_SGML Support Facilities- -Registration Procedures
         for Public Text Owner Identifiers,  Second Edition",
         April 1991, <http://www.ietf.org/proceedings/98dec/I-D/
         draft-ietf-calsch-icalfpi-00.txt>.

   [15]

   [TZDB]     "Time zone code and data, ftp://elsie.nci.nih.gov/pub/, updated
         periodically", data", October 2005,
              <ftp://elsie.nci.nih.gov/pub/>.

Authors' Addresses

   [VCAL]     Internet Mail Consortium, "vCalendar: The Electronic
              Calendaring and Scheduling Exchange Format",
              September 1996, <http://www.imc.org/pdi/vcal-10.txt>.

11.2.  Informative References

   [I-D.dusseault-caldav]
              Dusseault, L., "Calendaring Extensions to WebDAV
              (CalDAV)", draft-dusseault-caldav-12 (work in progress),
              April 2006.

URIs

   [1]  <mailto:ietf-calsify@osafoundation.org>

Author's Address

   Bernard Desruisseaux (editor)
   Oracle Corporation
   600 blvd. de Maisonneuve West
   Suite 1900
   Montreal, QC  H3A 3J2
   CA

   Email: bernard.desruisseaux@oracle.com
   URI:   http://www.oracle.com/

   Chris Stoner (editor)
   IBM
   5 Technology Park Drive
   Westford, MA  01886
   US

   Email: cstoner1@us.ibm.com
   URI:   http://www.ibm.com/

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