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Versions: 00 01 02

JSON data formats for iCalendar                               N. Jenkins
Internet-Draft                                               R. Stepanek
Intended status: Standards Track                                FastMail
Expires: February 10, 2018                                August 9, 2017


           JSCalendar: A JSON representation of calendar data
                      draft-jenkins-jscalendar-00

Abstract

   This specification defines a JSON representation of calendar data
   that can be used for storage and data exchange in a calendaring and
   scheduling environment.  It aims to be an alternative to the widely
   deployed iCalendar data format and to be unambiguous, extendable and
   simple to process.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on February 10, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   5
   2.  Structure of JSCalendar objects . . . . . . . . . . . . . . .   5
     2.1.  Type signatures . . . . . . . . . . . . . . . . . . . . .   6
     2.2.  Data Types  . . . . . . . . . . . . . . . . . . . . . . .   6
       2.2.1.  UTCDate . . . . . . . . . . . . . . . . . . . . . . .   6
       2.2.2.  LocalDate . . . . . . . . . . . . . . . . . . . . . .   6
       2.2.3.  Duration  . . . . . . . . . . . . . . . . . . . . . .   6
       2.2.4.  PatchObject . . . . . . . . . . . . . . . . . . . . .   7
     2.3.  Custom property extensions and values . . . . . . . . . .   7
   3.  JSCalendar properties . . . . . . . . . . . . . . . . . . . .   8
     3.1.  Metadata properties . . . . . . . . . . . . . . . . . . .   8
       3.1.1.  @type . . . . . . . . . . . . . . . . . . . . . . . .   8
       3.1.2.  uid . . . . . . . . . . . . . . . . . . . . . . . . .   8
       3.1.3.  relatedTo . . . . . . . . . . . . . . . . . . . . . .   8
       3.1.4.  prodId  . . . . . . . . . . . . . . . . . . . . . . .   9
       3.1.5.  created . . . . . . . . . . . . . . . . . . . . . . .   9
       3.1.6.  updated . . . . . . . . . . . . . . . . . . . . . . .  10
       3.1.7.  sequence  . . . . . . . . . . . . . . . . . . . . . .  10
       3.1.8.  method  . . . . . . . . . . . . . . . . . . . . . . .  10
     3.2.  Time, duration and recurrence properties  . . . . . . . .  10
       3.2.1.  recurrenceRule  . . . . . . . . . . . . . . . . . . .  10
       3.2.2.  recurrenceOverrides . . . . . . . . . . . . . . . . .  12
     3.3.  What and where properties . . . . . . . . . . . . . . . .  13
       3.3.1.  title . . . . . . . . . . . . . . . . . . . . . . . .  13
       3.3.2.  description . . . . . . . . . . . . . . . . . . . . .  13
       3.3.3.  locations . . . . . . . . . . . . . . . . . . . . . .  13
       3.3.4.  links . . . . . . . . . . . . . . . . . . . . . . . .  15
       3.3.5.  locale  . . . . . . . . . . . . . . . . . . . . . . .  16
       3.3.6.  localizations . . . . . . . . . . . . . . . . . . . .  16
       3.3.7.  categories  . . . . . . . . . . . . . . . . . . . . .  17
       3.3.8.  keywords  . . . . . . . . . . . . . . . . . . . . . .  17
       3.3.9.  color . . . . . . . . . . . . . . . . . . . . . . . .  17
     3.4.  Sharing and scheduling properties . . . . . . . . . . . .  17
       3.4.1.  status  . . . . . . . . . . . . . . . . . . . . . . .  17
       3.4.2.  priority  . . . . . . . . . . . . . . . . . . . . . .  18
       3.4.3.  freeBusyStatus  . . . . . . . . . . . . . . . . . . .  18
       3.4.4.  privacy . . . . . . . . . . . . . . . . . . . . . . .  18
       3.4.5.  replyTo . . . . . . . . . . . . . . . . . . . . . . .  19
       3.4.6.  participants  . . . . . . . . . . . . . . . . . . . .  20
     3.5.  Alerts properties . . . . . . . . . . . . . . . . . . . .  23
       3.5.1.  useDefaultAlerts  . . . . . . . . . . . . . . . . . .  23
       3.5.2.  alerts  . . . . . . . . . . . . . . . . . . . . . . .  23
   4.  JSCalendar objects  . . . . . . . . . . . . . . . . . . . . .  25
     4.1.  JSEvent . . . . . . . . . . . . . . . . . . . . . . . . .  25
       4.1.1.  start . . . . . . . . . . . . . . . . . . . . . . . .  25



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       4.1.2.  timeZone  . . . . . . . . . . . . . . . . . . . . . .  25
       4.1.3.  duration  . . . . . . . . . . . . . . . . . . . . . .  26
       4.1.4.  isAllDay  . . . . . . . . . . . . . . . . . . . . . .  26
     4.2.  JSTask  . . . . . . . . . . . . . . . . . . . . . . . . .  26
       4.2.1.  due . . . . . . . . . . . . . . . . . . . . . . . . .  27
       4.2.2.  start . . . . . . . . . . . . . . . . . . . . . . . .  27
       4.2.3.  timeZone  . . . . . . . . . . . . . . . . . . . . . .  27
       4.2.4.  estimatedDuration . . . . . . . . . . . . . . . . . .  27
       4.2.5.  completed . . . . . . . . . . . . . . . . . . . . . .  27
       4.2.6.  isAllDay  . . . . . . . . . . . . . . . . . . . . . .  28
     4.3.  JSGroup . . . . . . . . . . . . . . . . . . . . . . . . .  28
       4.3.1.  entries . . . . . . . . . . . . . . . . . . . . . . .  29
       4.3.2.  source  . . . . . . . . . . . . . . . . . . . . . . .  29
   5.  Conversion from and to iCalendar  . . . . . . . . . . . . . .  29
     5.1.  JSEvent . . . . . . . . . . . . . . . . . . . . . . . . .  29
       5.1.1.  isAllDay  . . . . . . . . . . . . . . . . . . . . . .  29
       5.1.2.  start . . . . . . . . . . . . . . . . . . . . . . . .  29
       5.1.3.  timeZone  . . . . . . . . . . . . . . . . . . . . . .  30
       5.1.4.  duration  . . . . . . . . . . . . . . . . . . . . . .  30
     5.2.  JSTask  . . . . . . . . . . . . . . . . . . . . . . . . .  30
       5.2.1.  isAllDay  . . . . . . . . . . . . . . . . . . . . . .  30
       5.2.2.  due . . . . . . . . . . . . . . . . . . . . . . . . .  30
       5.2.3.  start . . . . . . . . . . . . . . . . . . . . . . . .  30
       5.2.4.  timeZone  . . . . . . . . . . . . . . . . . . . . . .  30
       5.2.5.  estimatedDuration . . . . . . . . . . . . . . . . . .  31
       5.2.6.  completed . . . . . . . . . . . . . . . . . . . . . .  31
     5.3.  JSGroup . . . . . . . . . . . . . . . . . . . . . . . . .  31
       5.3.1.  entries . . . . . . . . . . . . . . . . . . . . . . .  31
       5.3.2.  source  . . . . . . . . . . . . . . . . . . . . . . .  31
     5.4.  Common properties . . . . . . . . . . . . . . . . . . . .  31
       5.4.1.  alerts  . . . . . . . . . . . . . . . . . . . . . . .  31
       5.4.2.  categories  . . . . . . . . . . . . . . . . . . . . .  31
       5.4.3.  created . . . . . . . . . . . . . . . . . . . . . . .  32
       5.4.4.  description . . . . . . . . . . . . . . . . . . . . .  32
       5.4.5.  freeBusyStatus  . . . . . . . . . . . . . . . . . . .  32
       5.4.6.  keywords  . . . . . . . . . . . . . . . . . . . . . .  32
       5.4.7.  links . . . . . . . . . . . . . . . . . . . . . . . .  32
       5.4.8.  locale  . . . . . . . . . . . . . . . . . . . . . . .  32
       5.4.9.  localizations . . . . . . . . . . . . . . . . . . . .  32
       5.4.10. locations . . . . . . . . . . . . . . . . . . . . . .  32
       5.4.11. method  . . . . . . . . . . . . . . . . . . . . . . .  33
       5.4.12. participants  . . . . . . . . . . . . . . . . . . . .  33
       5.4.13. priority  . . . . . . . . . . . . . . . . . . . . . .  33
       5.4.14. privacy . . . . . . . . . . . . . . . . . . . . . . .  33
       5.4.15. prodId  . . . . . . . . . . . . . . . . . . . . . . .  33
       5.4.16. recurrenceOverrides . . . . . . . . . . . . . . . . .  33
       5.4.17. recurrenceRule  . . . . . . . . . . . . . . . . . . .  34
       5.4.18. relatedTo . . . . . . . . . . . . . . . . . . . . . .  34



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       5.4.19. replyTo . . . . . . . . . . . . . . . . . . . . . . .  34
       5.4.20. sequence  . . . . . . . . . . . . . . . . . . . . . .  34
       5.4.21. status  . . . . . . . . . . . . . . . . . . . . . . .  34
       5.4.22. title . . . . . . . . . . . . . . . . . . . . . . . .  34
       5.4.23. uid . . . . . . . . . . . . . . . . . . . . . . . . .  34
       5.4.24. updated . . . . . . . . . . . . . . . . . . . . . . .  34
   6.  JSCalendar object examples  . . . . . . . . . . . . . . . . .  34
     6.1.  Simple JSEvent  . . . . . . . . . . . . . . . . . . . . .  34
     6.2.  Recurring JSEvent with exception  . . . . . . . . . . . .  35
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  37
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  37
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  37
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  37
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  37
     10.2.  Informative References . . . . . . . . . . . . . . . . .  39
     10.3.  URIs . . . . . . . . . . . . . . . . . . . . . . . . . .  39
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  39

1.  Introduction

   The iCalendar data format[RFC5545], a widely deployed interchange
   format for calendaring and scheduling data, has served calendaring
   vendors for a long while, but contains some ambiguities and pitfalls
   that can not be overcome without backwards incompatible changes.

   For example, iCalendar defines various formats for local times, UTC
   time and dates, which shows to confuse new users.  Other sources for
   errors are the requirement for custom timezone definitions within a
   single calendar component, as well as the iCalendar format itself;
   the latter causing interoperability issues due to misuse of CR LF
   terminated strings, line continuations and subtle differences between
   iCalendar parsers.  Lastly, up until recently the iCalendar format
   did not allow to express the difference between two calendar
   components, which results in verbose exchanges during scheduling.

   Some of these issues were addressed by the jCal [RFC7265] format,
   which is a direct mapping between iCalendar and JSON.  However, it
   did not attempt to extend or update iCalendar semantics.

   This document defines a JSON-based format describing a single event
   or task object within a calendar, or a group of such objects, using a
   new data model that aims to be unambiguous, extendable and simple to
   process.

   The key design considerations for this format are as follows:






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   o  The attributes of the calendar entry represented must be described
      as a simple key-value pair, reducing complexity of its
      representation.

   o  The data format should avoid all ambiguities, making it difficult
      to make mistakes during implementation and increasing
      interoperability.

   o  Most of the initial set of attributes should be taken from the
      iCalendar data format, but a conversion between the data formats
      is not guaranteed to be completed without losing semantic meaning.

   o  Extensions, such as new properties and components, MUST NOT lead
      to requiring an update to this document.

   JSON is a text-based data interchange format as specified
   in[RFC7159].  The I-JSON format defined in [RFC7493] is a strict
   subset of this, adding restrictions to avoid potentially confusing
   scenarios (for example, it mandates that an object MUST NOT have two
   properties with the same key).  Using JSON allows to decrease
   interoperability issues and helps to speed up adoption due to its
   widespread adoption.

1.1.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   The underlying format used for this specification is JSON.
   Consequently, the terms "object" and "array" as well as the four
   primitive types (strings, numbers, booleans, and null) are to be
   interpreted as described in Section 1 of[RFC7159].

   Some examples in this document contain "partial" JSON documents used
   for illustrative purposes.  In these examples, three periods "..."
   are used to indicate a portion of the document that has been removed
   for compactness.

2.  Structure of JSCalendar objects

   A JSCalendar object is a JSON object, which MUST be valid I-JSON (a
   stricter subset of JSON), as specified in[RFC7159].  Property names
   and values are case-sensitive.

   The object has a collection of properties, as specified in the
   following sections.  Unless otherwise specified, all properties are




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   optional; omitted properties MUST be treated identically to if that
   property had the value of "null", unless otherwise specified.

2.1.  Type signatures

   Types signatures are given for all JSON objects in this document.
   The following conventions are used:

   o  "Boolean|String": The value is either a JSON "Boolean" value, or a
      JSON "String" value.

   o  "Foo": Any name that is not a native JSON type means an object for
      which the properties (and their types) are defined elsewhere
      within this document.

   o  "Foo[]": An array of objects of type "Foo".

   o  "String[Foo]": A JSON "Object" being used as a map (associative
      array), where all the values are of type "Foo".

2.2.  Data Types

   In addition to the standard JSON data types, the following data types
   are used in this specification:

2.2.1.  UTCDate

   This is a string in [RFC3339] "date-time" format, with the further
   restrictions that any letters MUST be in upper-case, the time
   component MUST be included and the time MUST be in UTC.  Fractional
   second values MUST NOT be included unless non-zero (so, for example
   "2010-10-10T10:10:10.003Z" is OK, but "2010-10-10T10:10:10.000Z" is
   invalid and MUST be encoded as "2010-10-10T10:10:10Z").

   In common notation, it should be of the form "YYYY-MM-DDTHH:MM:SSZ".

2.2.2.  LocalDate

   This is a date-time string _with no time zone/offset information_.
   It is otherwise in the same format as UTCDate: "YYYY-MM-DDTHH:MM:SS".
   The time zone to associate the LocalDate with comes from an
   associated property.

2.2.3.  Duration

   A duration is represented by a subset of ISO8601 duration format, as
   specified by the following ABNF:




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       dur-secfrac = "." 1*DIGIT
       dur-second  = 1*DIGIT [dur-secfrac] "S"
       dur-minute  = 1*DIGIT "M" [dur-second]
       dur-hour    = 1*DIGIT "H" [dur-minute]
       dur-time    = "T" (dur-hour / dur-minute / dur-second)
       dur-day     = 1*DIGIT "D"

       duration    = "P" (dur-day [dur-time] / dur-time)

   In addition, the duration MUST NOT include fractional second values
   unless the fraction is non-zero.

2.2.4.  PatchObject

   A *PatchObject* is of type "String[*|null]", and represents an
   unordered set of patches on a JSON object.  The keys are a path in a
   subset of [RFC6901] JSON pointer format, with an implicit leading "/"
   (i.e. prefix each key with "/" before applying the JSON pointer
   evaluation algorithm).

   The pointer MUST NOT reference inside an array (i.e. you MUST NOT
   insert/delete from an array; the array MUST be replaced in its
   entirety instead).  Any patch with a key that attempts to do this
   MUST be ignored.

   When evaluating a path, all parts prior to the last (i.e. the value
   after the final slash) MUST exist for the patch to be valid.  If not,
   the patch MUST be ignored.

   There MUST NOT be two patches in the PatchObject where the pointer of
   one is the prefix of the pointer of the other, e.g. "alerts/1/offset"
   and "alerts".  The result in this case is undefined.

   The value associated with each pointer is either:

   o  "null": Remove the property from the patched object.  If not
      present in the parent, this a no-op.

   o  Anything else: The value to replace the inherited property on the
      patch object with (if present) or add to the property (if not
      present).

2.3.  Custom property extensions and values

   Vendors MAY add additional properties to the calendar object to
   support their custom features.  The names of these properties SHOULD
   be prefixed with a domain name controlled by the vendor to avoid
   conflict, e.g. "fastmail.com/customprop".  Other systems that



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   interact with a JSCalendar object that contain properties they do not
   recognise SHOULD try to preserve them, but MUST otherwise ignore
   them.

   Some JSCalendar properties allow vendor-specific value extensions.
   If so, vendor specific values MUST be prefixed with a domain name
   controlled by the vendor, e.g. "fastmail.com/customrel", unless
   otherwise noted.

3.  JSCalendar properties

   JSCalendar objects share a set of properties, but not all JSCalendar
   support the same properties.  Refer to the respective object type
   definitions (Section 4) which common properties they support.

3.1.  Metadata properties

3.1.1.  @type

   Type: "String"

   Specifies the type which this object represents.

   A valid JSCalendar object MUST include this property.

3.1.2.  uid

   Type: "String"

   A globally unique identifier, used to associate the object as the
   same across different systems, calendars and views.  Note that all
   JSCalendar objects share the same id space, so there MUST NOT be two
   JSCalendar objects of different type with the same uid.

   A valid JSCalendar object MUST include this property.

3.1.3.  relatedTo

   Type: "String[Relation]|null"

   Relates the object to other objects of the same type.  This is
   represented as a map of the uid of the related object to information
   about the relation.

   A *Relation* object has the following properties:

   o  *relation*: "String[]" Describes how the linked object is related
      to this object.



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      The strings in the array MUST each be at most one of the following
      values, registered in a future RFC, or a vendor-specific value:

      *  "first": The linked object is the first in the series this
         object is part of.

      *  "next": The linked object is the next in the series this object
         is part of.

      *  "child": The linked object is a subpart of this object.

      *  "parent": This object is part of the overall linked object.

   If an object is split to make a "this and future" change to a
   recurrence, the original object should be truncated to end at the
   previous occurrence before this split, and a new object created to
   represent all the objects after the split.

   A "relation=["next"]" relatedTo property SHOULD be set on the
   original object with the uid of the new object.  A
   "relation=["first"]" relatedTo property with the UID of the first
   object in the series SHOULD be set on the new object.  Clients can
   then follow these UIDs to get the complete set of objects if the user
   wishes to modify them all at once.

3.1.4.  prodId

   Type: "String|null"

   The identifier for the product that created the JSCalendar object.

   The vendor of the implementation SHOULD ensure that this is a
   globally unique identifier, using some technique such as an FPI
   value, as defined in [ISO.9070.1991].

   This property SHOULD NOT be used to alter the interpretation of an
   JSCalendar object beyond the semantics specified in this document.
   For example, it is not to be used to further the understanding of
   non-standard properties.

3.1.5.  created

   Type: "UTCDate|null"

   The date and time this object was initially created.






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3.1.6.  updated

   Type: "UTCDate"

   The date and time the data in this object was last modified.

3.1.7.  sequence

   Type: "Number" (Defaults to "0" if omitted)

   Initially zero, this is monotonically incremented each time a
   significant change is made to the object.

3.1.8.  method

   Type: "String|null"

   The iTIP ([RFC5546]) method, in lower-case.  Used for scheduling.

3.2.  Time, duration and recurrence properties

3.2.1.  recurrenceRule

   Type: "Recurrence"

   Defines a recurrence rule (repeating pattern) for recurring calendar
   objects.

   A *Recurrence* object is a JSON object mapping of a RECUR value type
   in iCalendar, see [RFC5545] and[RFC7529].  Objects recur by applying
   the recurrence rule (and *recurrenceOverrides*) to the *start* date/
   time.  A JSTask (Section 4.2) without a *start* recurs by its *due*
   date/time, if defined.

   A Recurrence object has the following properties:

   o  *frequency*: "String" This MUST be one of the following values:

      *  "yearly"

      *  "monthly"

      *  "weekly"

      *  "daily"

      *  "hourly"




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      *  "minutely"

      *  "secondly"

      To convert from iCalendar, simply lower-case the FREQ part.

   o  *interval*: "Number"(optional, defaults to "1") The INTERVAL part
      from iCal.  If included, it MUST be an integer "x >= 1".

   o  *rscale*: "String"(optional, defaults to ""gregorian"") The RSCALE
      part from iCalendar RSCALE [RFC7529], converted to lower-case.

   o  *skip*: "String"(optional, defaults to ""omit"") The SKIP part
      from iCalendar RSCALE [RFC7529], converted to lower-case.

   o  *firstDayOfWeek*: "String"(optional, defaults to ""mo"") The WKST
      part from iCalendar, represented as a lower-case abbreviated two-
      letter English day of the week.  If included, it MUST be one of
      the following values: ""mo"|"tu"|"we"|"th"|"fr"|"sa"|"su"".

   o  *byDay*: "NDay[]"(optional) An *NDay* object has the following
      properties:

      *  *day*: "String" The day-of-the-week part of the BYDAY value in
         iCalendar, lower-cased.  MUST be one of the following values:
         ""mo"|"tu"|"we"|"th"|"fr"|"sa"|"su"".

      *  *nthOfPeriod*: "Number"(optional) If present, rather than
         representing every Friday (for example), it represents only a
         specific instance within the period (month for monthly
         recurrences, year for yearly recurrences).  Must be a non-zero
         integer, negative integers means nth-last of period.  This is
         the ""+1"" or ""-3" " etc. prefix from the BYDAY values in
         iCal.

   o  *byDate*: "Number[]"(optional) The BYMONTHDAY part from iCalendar.
      The array MUST have at least one entry if included.

   o  *byMonth*: "String[]"(optional) The BYMONTH part from iCalendar.
      Each entry is a string representation of a number, starting from
      "1" for the first month in the calendar (e.g. ""1" " means
      ""January"" with Gregorian calendar), with an optional ""L""
      suffix (see [RFC7529]) for leap months (this MUST be upper-case,
      e.g. ""3L"").  The array MUST have at least one entry if included.

   o  *byYearDay*: "Number[]"(optional) The BYYEARDAY part from
      iCalendar.  The array MUST have at least one entry if included.




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   o  *byWeekNo*: "Number[]"(optional) The BYWEEKNO part from iCalendar.
      The array MUST have at least one entry if included.

   o  *byHour*: "Number[]"(optional) The BYHOUR part from iCalendar.
      The array MUST have at least one entry if included.

   o  *byMinute*: "Number[]"(optional) The BYMINUTE part from iCalendar.
      The array MUST have at least one entry if included.

   o  *bySecond*: "Number[]"(optional) The BYSECOND part from iCalendar.
      The array MUST have at least one entry if included.

   o  *count*: "Number"(optional) The COUNT part from iCalendar.  This
      MUST NOT be included if an *until* property is specified.

   o  *until*: "LocalDate"(optional) The UNTIL part from iCalendar.
      This MUST NOT be included if a *count* property is specified.
      Note, as in iCalendar, this date is presumed to be in the timezone
      specified in *timeZone*. It is not a UTC time.

3.2.2.  recurrenceOverrides

   Type: "LocalDate[PatchObject|null]|null"

   The object is a map of the Recurrence-Id (i.e. the date-time of the
   start of the occurrence) to either "null", to indicate the occurrence
   should be deleted, or an object of patches to apply to the generated
   occurrence object.

   If the Recurrence-Id does not match an expanded start date from a
   recurrence rule, it is to be treated as an additional occurrence
   (like an RDATE from iCalendar).  The patch object may often be empty
   in this case.

   By default, an occurrence inherits all properties from the main event
   except the start (or due) date-time, which is shifted to the new
   start time.  However, individual properties of the occurrence can be
   modified by a patch, or multiple patches.

   A pointer in the PatchObject MUST NOT start with one of the following
   prefixes; any patch with such a key MUST be ignored:

   o  uid

   o  relatedTo

   o  prodId




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   o  method

   o  isAllDay

   o  recurrenceRule

   o  recurrenceOverrides

   o  replyTo

3.3.  What and where properties

3.3.1.  title

   Type: "String" (Defaults to the empty string if omitted)

   A short summary of the object.

3.3.2.  description

   Type: "String" (Defaults to the empty string if omitted)

   A longer form description of the object.  This is plain text, but a
   client SHOULD attempt to hyperlink URLs when displaying it.

3.3.3.  locations

   Type: "String[Location]|null"

   A map of of location id to Location objects, representing locations
   associated with the object.  A location id may be any string and need
   only be unique to this object, although a UUID is a practical choice.

   A *Location* object has the following properties.  All properties are
   optional, but every Location object MUST have at least one property:

   o  *name*: "String" The human-readable name of the location.

   o  *description*: "String" Human-readable instructions for accessing
      this location.  This may be an address, set of directions, door
      access code, etc.

   o  *rel*: "String" The relation type of this location to the
      JSCalendar object.

      This MUST be either one of the following values, registered in a
      future RFC, or a vendor-specific value.  Any value the client or
      server doesn't understand should be treated the same as "unknown".



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      *  "start": The JSCalendar object starts at this location.

      *  "end": The JSCalendar object ends at this location.

      *  "virtual": This is not a physical location (e.g. this location
         is an online chat room where people will meet).

      *  "unknown": The relation of this location to the event is
         unknown.

   o  *features*: "String[]|null" The features supported by this
      location.

      The strings in the array MUST each be either one of the following
      values, registered in a future RFC, or a vendor-specific value.
      Any value the client or server doesn't understand should be
      ignored, but preserved.

      The features supported by locations with rel-type "virtual" are:

      *  "audio": audio capability

      *  "chat": chat or instant messaging

      *  "feed": a blog or Atom feed

      *  "moderator": moderator-specific

      *  "phone": phone conference

      *  "screen": screen sharing

      *  "video": video conferencing

      *  any vendor-prefixed custom value

   o  *timeZone*: "String" A time zone for this location.

      If omitted, the start time zone MUST be used for this location.

   o  *coordinates*: "String" An [RFC5870] "geo:" URI for the location.

   o  *uri*: "String" A URI that represents how to connect from this
      location.

      This may be a telephone number (represented as
      "tel:+1-555-555-555") for a teleconference, a web address for




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      online chat, or a custom URI for something like Skype (e.g.
      "skype:username").

   o  *linkIds*: "String[]|null" Links to alternate representations of
      this location.

      For example, an alternative representation could be in vCard
      format.  If a given value does not correspond to any link id in
      the links property of the instance, this MUST be ignored.

3.3.4.  links

   Type: "String[Link]|null"

   A map of of link id to Link objects, representing external resources
   associated with the object.  A link id may be any string and need
   only be unique to this object, although the href or a UUID are
   practical choices.

   A *Link* object has the following properties:

   o  *href*: "String" A URI from which the resource may be fetched.

      This MAY be a "data:" URL, but it is recommended that the file be
      hosted on a server.

   o  *type*: "String|null"(optional, defaults to "null") The content-
      type of the resource, if known.

   o  *size*: "Number|null"(optional, defaults to "null") The size, in
      bytes, of the resource when fully decoded (i.e. the number of
      bytes in the file the user would download), if known.

   o  *rel*: "String"(optional, defaults to "related") Identifies the
      relation of the linked resource to the object.  The value MUST be
      a registered relation type (see[RFC5988]).

      The features supported by locations with rel-type "virtual" are:

      Links with a rel of "enclosure" SHOULD be considered by the client
      as attachments for download.

      Links with a rel of "describedby" SHOULD be considered by the
      client to be an alternate representation of the description, for
      example an HTML page describing the object.

      Links with a rel of "icon" SHOULD be considered by the client to
      be an image that it MAY use when presenting the calendar data to a



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      user.  The properties object of this link MAY include a display
      property indicating the intended purpose of this image.  If
      included, the value MUST be either one of the following values,
      registered in a future RFC, or a vendor-specific value.

      *  "badge": an image inline with the title of the object

      *  "graphic": a full image replacement for the object itself

      *  "fullsize": an image that is used to enhance the object

      *  "thumbnail": a smaller variant of "fullsize " to be used when
         space for the image is constrained

   o  *title*: "String|null"(optional, defaults to "null") A human-
      readable description of the resource.

   o  *properties*: "String[String|null]|null"(optional, defaults to
      "null") Extra metadata stored by a client about a link.

      The keys are as defined in this document, as defined in a future
      RFC, or URIs that should be owned by the client author to avoid
      conflicts.

3.3.5.  locale

   Type: "String|null"

   The [RFC5646] language tag that best describes the locale used for
   the event, if known.

3.3.6.  localizations

   Type: "String[PatchObject]|null"

   A map of [RFC5646] language tag to a patch object which localises the
   event into that locale.

   See the description of PatchObject (Section 2.2.4) for the structure
   of the PatchObject.  The patches are applied to the top-level object.
   In addition to all the restrictions on patches specified there, the
   pointer also MUST NOT start with one of the following prefixes; any
   patch with a such a key MUST be ignored:

   o  sequence

   o  localization




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   o  start

   o  timeZone

   o  duration

   o  status

   o  freeBusyStatus

   o  participants

   o  useDefaultAlerts

3.3.7.  categories

   Type: "String[]|null"

   Specifies the categories related to the calendar object.  Array
   values MUST be URIs.

3.3.8.  keywords

   Type: "String[]|null"

   A list of keywords or tags related to the object.  The values are
   freeform and do not have to follow any particular structure.

3.3.9.  color

   Type: "String"

   Specifies a color clients MAY use when displaying this event.  The
   value is a case-insensitive color name taken from the CSS3 set of
   names, defined in Section 4.3 of W3C.REC-css3-color-20110607 [1].  It
   is not intended that clients necessarily use the exact RGB value
   associated with this color name, but rather that they use the name to
   find a suitable color that works in the given UA context.

3.4.  Sharing and scheduling properties

3.4.1.  status

   Type: "String"(defaults to ""confirmed"" if omitted)

   The status of the object.  MUST be one of:

   o  "confirmed": Indicates the calendar object is definite.



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   o  "cancelled": Indicates the calendar object was cancelled.

   o  "tentative": Indicates the calendar object is tentative.

3.4.2.  priority

   Type: "Number"(defaults to "0" if omitted)

   Specifies a priority for the event.  This may be used as part of
   scheduling systems to help resolve conflicts for a time period.

   The priority is specified as an integer in the range 0 to 9.  A value
   of 0 specifies an undefined priority.  A value of 1 is the highest
   priority.  A value of 2 is the second highest priority.  Subsequent
   numbers specify a decreasing ordinal priority.  A value of 9 is the
   lowest priority.  Other integer values are reserved for future use.

3.4.3.  freeBusyStatus

   Type: "String"(defaults to "busy" if omitted)

   Specifies how this property should be treated when calculating free-
   busy state.  The value MUST be one of:

   o  ""free"": The object should be ignored when calculating whether
      the user is busy.

   o  ""busy"": The object should be included when calculating whether
      the user is busy.

3.4.4.  privacy

   Type: "String"(defaults to "public" if omitted)

   Calendar objects are normally collected together and may be shared
   with other users.  The privacy property allows the object owner to
   indicate that it should not be shared, or should only have the time
   information shared but the details withheld.

   As JSCalendar is simply a data model, enforcement of the restrictions
   indicated by this property are up to the implementations.

   This property MUST NOT affect the information sent to scheduled
   participants; it is only interpreted when the object is shared as
   part of a shared calendar.

   The value MUST be either one of the following values, registered in a
   future RFC, or a vendor-specific value.  Vendor specific values MUST



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   be prefixed with a domain name controlled by the vendor, e.g.
   "fastmail.com/topsecret".  Any value the client or server doesn't
   understand should be preserved but treated as equivalent to
   "private".

   o  "public": The full details of the object are visible to those whom
      the object's calendar is shared with.

   o  "private": The details of the object are hidden; only the basic
      time and metadata is shared.  Implementations SHOULD ensure the
      following properties are stripped when the object is accessed by a
      sharee:

      *  title

      *  description

      *  locations

      *  links

      *  locale

      *  localizations

      *  participants

      *  replyTo

      In addition, any patches in "recurrenceOverrides" whose key is
      prefixed with one of the above properties SHOULD be stripped.

   o  "secret": The object is hidden completely (as though it did not
      exist) when the calendar is shared.

3.4.5.  replyTo

   Type: "String[String]|null"

   Represents methods by which a participant may RSVP to the organizer
   of the calendar object.  The keys in the property value are the
   available methods.  The value is a URI to use that method.  Future
   methods may be defined in future specications; a calendar client MUST
   just ignore any method it does not understand.

   The following methods are defined:





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   o  "imip": The organizer accepts an iMIP [RFC6047] response.  The
      value MUST be a "mailto:" URI.

   o  "web": There is a web page where the user may submit an RSVP using
      their browser.  The value MUST be an "http:" or "https: " URI.

3.4.6.  participants

   Type: "String[Participant]|null"

   A map of participant id to a participant describing their
   participation in the calendar object.  A participant id may be any
   string and need only be unique to this event; the email address of
   the participant is a good choice.

   A *Participant* object has the following properties.  Properties are
   mandatory unless marked otherwise:

   o  *name*: "String" The display name of the participant (e.g.  "Joe
      Bloggs").

   o  *email*: "String" The email address for the participant.

   o  *kind*: "String"(optional, defaults to "unknown") What kind of
      entity this participant is.

      This MUST be either one of the following values, registered in a
      future RFC, or a vendor-specific value.  Any value the client or
      server doesn't understand should be treated the same as "unknown".

      *  "individual": a single person

      *  "group": a collection of people invited as a whole

      *  "resource": a non-human resource, e.g. a projector

      *  "location": a physical location involved in the event that
         needs to be scheduled, e.g. a conference room.

      *  "unknown": no information is available about the kind of this
         participant.

   o  *roles*: "String[]" A list of roles that this participant fulfils.

      At least one value MUST be specified for the participant.  This
      MUST be either one of the following values, registered in a future
      RFC, or a vendor-specific value.  Any value the client or server
      doesn't understand should be preserved but ignored.



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      *  "owner": The participant is an organizer of the event, and
         allowed to make alterations to any part of the event.

      *  "attendee": The participant is an attendee of the event.

      *  "chair": The participant is in charge of the event when it
         occurs.

   o  *locationId|null*: "String"(optional, defaults to "null") The
      location at which this participant is expected to be attending.

      If the value does not correspond to any location id in the
      locations property of the instance, this MUST be treated the same
      as if the participant's locationId were specified as null.

   o  *rsvpResponse*: "String"(optional, defaults to "needs-action") The
      RSVP response, if any, of this participant.

      The value MUST be either one of the following values, registered
      in a future RFC, or a vendor-specific value:

      *  "needs-action": No status yet set by the participant.

      *  "accepted": The participant will attend.

      *  "declined": The participant may attend.

      *  "tentative": The participant will not attend.

   o  *participation*: "String"(optional, defaults to "required") The
      required attendance of this participant.

      The value MUST be either one of the following values, registered
      in a future RFC, or a vendor-specific value.  Any value the client
      or server doesn't understand should be treated the same as
      "required".

      *  "non-participant": Indicates a participant who is copied for
         information purposes only.

      *  "optional": Indicates a participant whose participation is
         optional.

      *  "required": Indicates a participant whose participation is
         required.






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   o  *rsvpWanted*: "Boolean"(optional, defaults to "false") If true,
      the organizer is expecting the participant to notify them of their
      status.

   o  *scheduleSequence*: "Number"(optional, defaults to "0") The
      sequence number of the last response from the participant.

      This can be used to determine whether the partcipant has sent a
      new RSVP following significant changes to the event, and to
      determine if future responses are responding to a current or older
      view of the data.

   o  *scheduleUpdated*: "UTCDate|null"(optional, defaults to "null")
      The *updated* property of the last iMIP response from the
      participant.

      This can be compared to the *updated* timestamp in future iMIP
      responses to determine if the response is older or newer than the
      current data.

   o  *invitedBy*: "String|null"(optional, defaults to "null") The
      participant id of the participant who invited this one, if known.

   o  *delegatedTo*: "String[]|null"(optional, defaults to "null") A
      list of participant ids of participants that this participant has
      delegated their participation to.  This MUST be omitted if none
      (rather than an empty array).

   o  *delegatedFrom*: "String[]|null"(optional, defaults to "null") A
      list of participant ids that this participant is acting as a
      delegate for.  This MUST be omitted if none (rather than an empty
      array).

   o  *memberOf*: "String[]|null"(optional, defaults to "null") A list
      of group addresses that were invited to this calendar object,
      which caused this participant to be invited due to their
      membership of the group(s).  This MUST be omitted if none (rather
      than an empty array).

   o  *linkIds*: "String[]|null"(optional, defaults to "null") Links to
      more information about this participant, for example in vCard
      format.  If a given value does not correspond to any link id in
      the links property of the instance, this id MUST be ignored.  This
      MUST be omitted if none (rather than an empty array).







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3.5.  Alerts properties

3.5.1.  useDefaultAlerts

   Type: "Boolean" (defaults to "false" if omitted)

   If "true", use the user's default alerts for this event and ignore
   the Section 3.5.2 property.  Fetching user defaults is dependent on
   the API from which this JSCalendar object is being fetched, and is
   not defined in this specification.

3.5.2.  alerts

   Type: "String[Alert]|null"

   A map of of alert id to Alert objects, representing alerts/reminders
   to display or send the user for this calendar object.  An alert id
   may be any string and need only be unique to this calendar object,
   although a UUID is a practical choice.

   An *Alert* Object has the following properties:

   o  *relativeTo*: "String" (optional, defaults to "before-start")
      Specifies where the offset is relative to for the alarm to
      trigger.  The value MUST be one of:

      *  "before-start"

      *  "after-start"

      *  "before-end"

      *  "after-end"

   o  *offset*: "Duration" The offset from the start and end/due of the
      calendar object to fire the alert.  Note, if the calendar object
      is in floating time (including all-day events), the server SHOULD
      use the user's default time zone when determining the offset.

   o  *action*: "DisplayAction|EmailAction|UnknownAction"

      Describes how to alert the user.

      A *DisplayAction* means a message (which is service dependent, but
      SHOULD include the summary and start or due time of the calendar
      object) SHOULD be shown to the user on any client connected to
      this account at the specified time.  How this message is formatted




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      (and any sound or other method of drawing the user's attention) is
      client specific.  It has the following properties:

      *  *type*: "String" The value MUST be "display".

      *  *acknowledged*: "UTCDate|null " (optional)

         When the user has permanently dismissed the alert the client
         SHOULD set this to the current time in UTC.  Other clients
         which sync this property can then automatically dismiss or
         suppress duplicate alerts (alerts with the same alert id that
         triggered on or before this date-time).

         For a recurring event, the *acknowledged* property of the
         parent event SHOULD be updated, unless the alert is already
         overridden in *recurrenceOverrides*.

      *  *snoozed*: "UTCDate|null" (optional)

         If the user temporarily dismisses the alert, this is the UTC
         date-time after which it should be reshown Clients displaying
         this alert SHOULD hide it if the snoozed property is updated to
         a time in the future.  When that time is reached, the alert
         SHOULD be reshown unless acknowledged is now after the original
         trigger time.

      *  *audioLinkId*: "String|null " (optional)

         The id of a link in the Section 3.3.4 property.  If the linked
         file is of an audio type understood by the client, the client
         SHOULD play this audio when triggering the alert.

      An *EmailAction* means the server MUST send an email as specified
      in the object at the specified time.  It has the following
      properties:

      *  *type*: "String" The value MUST be "email".

      *  *to*: "Emailer[]" An array of name/email objects to send the
         alert to.

         An *Emailer* object has the following properties:

         +  name: String The name of the recipient.  If not known,
            clients SHOULD use the empty string.

         +  email: String The email address of the recipient.




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      *  *subject*: "String" (optional) The subject to use for the
         email.  If omitted, this is implementation specific, but the
         server SHOULD try to choose an appropriate subject (such as
         "Event Summary: starting in 5 min").

      *  *textBody*: "String" (optional) The plain-text body to use for
         the email.  If omitted, the body of the email is implementation
         specific, but the server SHOULD include all pertinent details
         about the event, such as summary, location and start time.

      An *UnknownAction* object is an object that contains a _type _
      property whose value is not "email" or "string", plus zero or more
      other properties.  This is for compatibility with client
      extensions and future RFCs.  The client or server SHOULD NOT
      trigger any type of alert for action types they do not understand,
      but MUST preserve them.

4.  JSCalendar objects

4.1.  JSEvent

   MIME type: "application/json+cal;type=event"

   A JSEvent represents a scheduled amount of time on a calendar,
   typically a meeting, appointment, reminder or anniversary.  Multiple
   participants may partake in the event at multiple locations.

   A JSEvent @type (Section 3.1.1) property value MUST be "event".

   In addition to the common JSCalendar object properties (Section 3) a
   JSEvent has the following properties:

4.1.1.  start

   Type: "LocalDate" e.g.  "2015-09-02T00:00:00"

   The date/time the event would start in the event's time zone.

   A valid JSEvent MUST include this property.

4.1.2.  timeZone

   Type: "String|null"

   The IANA Time Zone Database [2] name for the time zone the event is
   scheduled in, or "null" for floating time.  If omitted, this MUST be
   presumed to be "null" (i.e. floating time).




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4.1.3.  duration

   Type: "Duration", e.g.  "P2DT3H" (Defaults to "P0D" if omitted)

   The zero or positive duration of the event in absolute time (i.e. in
   UTC time; ignoring DST shifts).  To get the end date in the event
   time zone, convert start into UTC, then add the duration, then
   convert the result into the appropriate time zone.

   A JSEvent MAY be end in a different timezone (e.g. a plane flight
   crossing timezones).  In this case, the JSEvent SHOULD specify the
   end timezone in a *location* property value that defines its *rel* to
   be "end" and the end timezone in its *timeZone* property.

4.1.4.  isAllDay

   Type: "Boolean" (optional, defaults to "false")

   Specifies if the event an all day event, such as a birthday or public
   holiday.

   If *isAllDay* is true, then the following restrictions apply:

   o  the *start* property MUST have a time component of "T00:00:00".

   o  the *timeZone* property MUST be null (or omitted).

   o  the *duration* property MUST only include a day component.

4.2.  JSTask

   MIME type: "application/json+cal;type=task"

   A JSTask represents an action-item, assignment, to-do or work item .

   A JSTask @type (Section 3.1.1) property value MUST be "task".

   A JSTask may start and be due at certain points in time, may take
   some estimated time to complete and may recur; none of which is
   required.  This notably differs from JSEvent (Section 4.1) which is
   required to start at a certain point in time and typically takes some
   non-zero duration to complete.

   In addition to the common JSCalendar object properties (Section 3) as
   JSTask has the following properties:






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4.2.1.  due

   Type: "LocalDate|null" e.g.  "2015-09-02T00:00:00"

   The date/time the task is due in the task's time zone.

4.2.2.  start

   Type: "LocalDate|null" e.g.  "2015-09-02T00:00:00"

   The date/time the task should start in the task's time zone.

   If the *due* property is set, the *start* property value MUST be
   earlier than or at the due date/time.

4.2.3.  timeZone

   Type: "String|null"

   The IANA Time Zone Database name for the time zone the task is
   scheduled in, or "null" for floating time.  If omitted, this MUST be
   presumed to be "null" (i.e. floating time).

4.2.4.  estimatedDuration

   Type: "Duration|null", e.g.  "P2DT3H"

   Specifies the estimated positive duration of time the task takes to
   complete.

   If the *start* and *due* properties are set, the estimated duration
   SHOULD be less than or equal to the time interval between these
   properties.

4.2.5.  completed

   Type: "UTCDate|null", e.g.  "2016-06-13T12:00:00Z"

   Specifies the date/time the task was completed.

   If the task is recurring and has future instances, a client may want
   to denote a specific task recurrence as completed but leave other
   instances as uncompleted.  One way to achieve this is by overriding
   the completed property in the task recurrence overrides
   (Section 3.2.2).  However, this could produce a long list of
   completion times for regularly recurring tasks.  An alternative
   approach is to split the JSTask into a current, single instance of
   JSTask with this instance completion time and a future recurring



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   instance.  Also see the definition of the relatedTo (Section 3.1.3)
   property Section 3.1.3 on splitting.

4.2.6.  isAllDay

   Type: "Boolean" (optional, defaults to "false")

   Specifies if the task is an all day task.

   If *isAllDay* is true, then the following restrictions apply:

   o  the *start* and *due* properties MUST have a time component of
      "T00:00:00".

   o  the *timeZone* property MUST be null (or omitted).

   o  the *duration* and *estimatedDuration* properties MUST only
      include a day component.

4.3.  JSGroup

   MIME type: "application/json+cal;type=group"

   A JSGroup is a collection of JSEvent (Section 4.1) and JSTask
   (Section 4.2) objects.  Typically, objects are grouped by topic (e.g.
   by keywords) or calendar membership.

   Its @type (Section 3.1.1) property value MUST be "group".

   JSGroup supports the following JSCalendar properties (Section 3):

   o  @type

   o  uid

   o  updated

   o  categories

   o  keywords

   o  name

   o  description

   o  color

   o  links



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   as well as the following JSGroup-specific properties:

4.3.1.  entries

   Type: "(JSTask|JSEvent)[]|null"

   A list of group members.  The list MAY contain multiple object types
   and implementations MUST ignore entries of unknown type.  The
   property value MUST either be "null" or the list MUST NOT be empty.

4.3.2.  source

   Type: "String|null" (optional, default is "null")

   The source from which updated versions of this group may be retrieved
   from.  If the value is not "null", it MUST be an URI.

5.  Conversion from and to iCalendar

   This section specifies which JSCalendar properties can be mapped from
   and to iCalendar format.  Implementations SHOULD follow these
   conversion guidelines.  Still, JSCalendar does not restrict itself to
   the expressivity of iCalendar and conversion between these two
   formats MAY be lossy.  Implementations that serve the same calendar
   entry in both JSCalendar and iCalendar SHOULD preserve properties
   that can not be converted (e.g., a JSCalendar property that can't be
   translated to iCalendar MAY be omitted in the iCalendar
   representation but MUST be preserved in the JSCalendar format).

5.1.  JSEvent

   The iCalendar counterpart to *JSEvent* is the VEVENT component type
   [RFC5545].  A VEVENT component that is a direct child of a VCALENDAR
   component is equivalent to a standalone JSEvent.  A VEVENT component
   *within* a VEVENT maps to the entries of the JSEvent
   *recurrenceOverrides* property (see Section 3.2.2).

5.1.1.  isAllDay

   Corresponds to the type (DATE or DATE-TIME) of the DTSTART property
   in iCalendar.

5.1.2.  start

   Corresponds to the DTSTART property in iCalendar.  Note that time
   zone information is stored separately in JSEvent.





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5.1.3.  timeZone

   Corresponds to the TZID part of the DTSTART property in iCalendar.

   If the event has a different end time zone to start time zone, this
   should be added as a JSCalendar *location* with just a *timeZone*
   property and "rel="end"".

5.1.4.  duration

   Corresponds to the DURATION or DSTART+DTEND properties in iCalendar.

5.2.  JSTask

   The iCalendar counterpart to *JSTask* is the VTODO component type
   [RFC5545].  A VTODO component that is a direct child of a VCALENDAR
   component is equivalent to a standalone JSTask.  A VTODO component
   *within* a master VTODO maps to the entries of the JSTask
   *recurrenceOverrides* property (see Section 3.2.2).

5.2.1.  isAllDay

   Corresponds to the type (DATE or DATE-TIME) of the DTSTART and DUE
   properties in iCalendar.

5.2.2.  due

   Corresponds to the DUE and DTSTART+DURATION properties in iCalendar.
   When mapping iCalendar VTODOs with DTSTART+DURATION, the due date is
   the result of adding DURATION to DTSTART in the DTSTART timezone.

5.2.3.  start

   Corresponds to the DTSTART property in iCalendar.

5.2.4.  timeZone

   Corresponds to the TZID part of the DTSTART/DUE properties in
   iCalendar.

   If the task has a different end time zone to start or due time zone,
   this should be added as a JSCalendar *location* with just a
   *timeZone* property and "rel="end"".








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5.2.5.  estimatedDuration

   Corresponds to the ESTIMATED-DURATION iCalendar property.  *NON-
   STANDARD*: this property is currently non-standard, see
   [draft-apthorp-ical-tasks].

5.2.6.  completed

   Maps to the COMPLETED iCalendar property.

5.3.  JSGroup

   A JSGroup converts to a iCalendar VCALENDAR containing VEVENT or
   VTODO components.

5.3.1.  entries

   The VEVENT and VTODO components within a top-level VCALENDAR
   component.

5.3.2.  source

   Corresponds to the SOURCE property in iCalendar.

5.4.  Common properties

5.4.1.  alerts

   An *Alert* corresponds to the VALARM component in iCalendar, where
   the *action* is determined by the iCalendar ACTION property value
   (e.g., a "DISPLAY" property indicates that the JSCalendar Alert
   action is a *DisplayAction* and similarly an iCalendar "EMAIL" value
   for *EmailAction* action).  The *relativeTo* and *offset* properties
   corresponds to the iCalendar TRIGGER property.

   *NON-STANDARD*: The iCalendar properties for JSCalendar Alert actions
   are non-standard, see [draft-daboo-valarm-extensions].

5.4.2.  categories

   Corresponds to the STRUCTURED-CATEGORY property in iCalendar, see.
   *NON-STANDARD*: this property is currently non-standard, see
   [draft-ietf-calext-ical-relations].








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5.4.3.  created

   Corresponds to the CREATED property in iCalendar.

5.4.4.  description

   Corresponds to the DESCRIPTION property in iCalendar.

5.4.5.  freeBusyStatus

   Corresponds to the TRANSP property in iCalendar.

5.4.6.  keywords

   Corresponds to the COLOR property in iCalendar, as specified in
   [RFC7986].

5.4.7.  links

   Corresponds to the ATTACH ([RFC5545]) and IMAGE iCalendar properties
   ([RFC7986]).

5.4.8.  locale

   Corresponds to the LANGUAGE parameter in iCalendar, which is added to
   individual properties.  When converting from iCalendar, one language
   must be picked as the main locale for the object, and all properties
   in other languages moved to the localizations JSEvent property.

5.4.9.  localizations

   Corresponds to the LANGUAGE parameter in iCalendar, which is added to
   individual properties.  When converting from iCalendar, one language
   must be picked as the main locale for the object, and all properties
   in other languages moved to the localizations JSEvent property.

5.4.10.  locations

   Corresponds to the LOCATION and CONFERENCE [RFC7986] properties in
   iCalendar.  For LOCATION, the JSCalendar representation is much
   richer than is supported by iCalendar.  When converting from
   iCalendar, the LOCATION property should become a single location with
   just a description property.  CONFERENCE property values in iCalendar
   map to locations with rel type "virtual".

   A location *feature* property value corresponds to the FEATURE
   property parameter values defined in [RFC7986].




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5.4.11.  method

   Corresponds to the METHOD property in iCalendar.

5.4.12.  participants

   Corresponds to the ORGANIZER and ATTENDEES properties from iCalendar.
   The following Participant object fields map to iCalendar parameters
   on the ORGANIZER and ATTENDEE properties:

   o  *name*: the CN parameter

   o  *kind*: the CUTYPE parameter

   o  *rsvpResponse*: the PARTSTAT parameter

   o  *participation*: the ROLE parameter

   o  *rsvpWanted*: the RSVP parameter

   o  *delegatedTo*: the DELEGATED-TO parameter

   o  *delegatedFrom*: the DELEGATED-FROM parameter

   o  *memberOf*: the MEMBER parameter

   The *scheduleSequence* and *scheduleUpdated * properties correspond
   to the iCalendar SEQUENCE and DTSTAMP property values for the
   participant's latest iMIP message.

5.4.13.  priority

   Corresponds to the PRIORITY property in iCalendar.

5.4.14.  privacy

   Corresponds to the CLASS property in iCalendar.

5.4.15.  prodId

   Corresponds to the PRODID property in iCalendar.

5.4.16.  recurrenceOverrides

   Corresponds to the RDATE and EXDATE properties in iCalendar, plus
   VEVENT (for JSEvent) or VTODO (for JSTask) instances with a
   Recurrence-Id.




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5.4.17.  recurrenceRule

   Corresponds to the RRULE property in iCalendar.  See the property
   definition at section Section 3.2.1 how to map a RRULE value.

5.4.18.  relatedTo

   Corresponds to the RELATED-TO property in iCalendar.

5.4.19.  replyTo

   A *replyTo* property of type "imip" corresponds to the email address
   of the ORGANIZER property in iCalendar.  There is no iCalendar
   representation for the "web" type.

5.4.20.  sequence

   Corresponds to the SEQUENCE property in iCalendar.

5.4.21.  status

   Corresponds to the STATUS property in iCalendar (converted to lower-
   case).

5.4.22.  title

   Corresponds to the SUMMARY property in iCalendar.

5.4.23.  uid

   Corresponds to the UID property in iCalendar.

5.4.24.  updated

   Corresponds to the DTSTAMP and LAST-MODIFIED properties in iCalendar.
   (These are only different in the iTIP case, and the difference is not
   actually useful.)

6.  JSCalendar object examples

   The following examples illustrate several aspects of the JSCalendar
   data model and foramt.

6.1.  Simple JSEvent

   This JSEvent object represents a one-time event taking place on
   September 28 at 4pm, GMT for one hour.




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       {
           "@type": "event",
           "uid": "2a358cee-6489-4f14-a57f-c104db4dc357",
           "updated": "2016-09-14T13:24:34Z",
           "title": "Squash",
           "description": "",
           "start": "2016-09-28T16:00:00",
           "timeZone": "Etc/UTC",
           "duration": "PT1H",
           "recurrenceRule": null,
           "recurrenceOverrides": null,
           "freeBusyStatus": "free",
           "replyTo": null,
           "participants": null,
           "alerts": null,
           "links": null,
           "locations": null,
           "locale": "en",
           "localizations": null,
       }

6.2.  Recurring JSEvent with exception

   This JSEvent object represents a recurring event, taking place the
   first time on January 1, 2016 at 1pm.  It recurs monthly, but does
   not occur on February 2, 2016.  In addition to the regular
   recurrences it also occurs on December 5, 2016 at 5pm.  On May 1, it
   takes place at another location.























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      {
         "@type": "event",
         "uid": "89eee195-600b-423b-b3a6-52b3a420e556",
         "title": "Tennis",
         "locations": {
               "loc1" : {
                    "description" : "Joe's Tennis Plaza, Court #1"
               }
         },
         "isAllDay": false,
         "start": "2016-01-01T13:00:00",
         "timeZone": "Europe/Vienna",
         "duration": "PT1H",
         "recurrenceRule": {
           "frequency": "monthly",
           "rscale": "gregorian"
         },
         "recurrenceOverrides": {
           "2016-12-05T17:00:00": {},
           "2016-02-01T13:00:00": null,
           "2016-05-01T13:00:00": {
             "duration": "PT2H",
             "locations": {
               "loc2": {
                   "description": "Tennis Fritz&Mayer, Ltd."
               }
             }
           }
         }
       }

   Note that the recurrenceOverride on May 1 overrides the complete
   location object.  If the event should occur at *both* locations, the
   PatchObject would be defined as follows:

      {
         [...]
         "recurrenceOverrides": {
           [...]
           "2016-05-01T13:00:00": {
             "duration": "PT2H",
             "locations/loc2": {
                   "description": "Tennis Fritz&Mayer, Ltd."
             }
           }
         }





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7.  Security Considerations

   The use of JSON as a format does have its own inherent security risks
   as discussed in Section 12 of [RFC7159].  Even though JSON is
   considered a safe subset of JavaScript, it should be kept in mind
   that a flaw in the parser processing JSON could still impose a
   threat, which doesn't arise with conventional iCalendar data.

   With this in mind, a parser for JSON data aware of the security
   implications should be used for the format described in this
   document.  For example, the use of JavaScript's "eval()" function is
   considered an unacceptable security risk, as described in Section 12
   of[RFC7159].  A native parser with full awareness of the JSON format
   should be preferred.

8.  IANA Considerations

   This document defines a MIME media type for use with iCalendar in
   JSON data.  This media type SHOULD be used for the transfer of
   calendaring data in JSON.

9.  Acknowledgments

   The author would like to thank the following for their valuable
   contributions: (TODO:names).  This specification originated from the
   work of the API technical committee of CalConnect, the Calendaring
   and Scheduling Consortium.

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
              <http://www.rfc-editor.org/info/rfc3339>.

   [RFC5545]  Desruisseaux, B., Ed., "Internet Calendaring and
              Scheduling Core Object Specification (iCalendar)",
              RFC 5545, DOI 10.17487/RFC5545, September 2009,
              <http://www.rfc-editor.org/info/rfc5545>.






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   [RFC5546]  Daboo, C., Ed., "iCalendar Transport-Independent
              Interoperability Protocol (iTIP)", RFC 5546,
              DOI 10.17487/RFC5546, December 2009,
              <http://www.rfc-editor.org/info/rfc5546>.

   [RFC5646]  Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
              Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646,
              September 2009, <http://www.rfc-editor.org/info/rfc5646>.

   [RFC5870]  Mayrhofer, A. and C. Spanring, "A Uniform Resource
              Identifier for Geographic Locations ('geo' URI)",
              RFC 5870, DOI 10.17487/RFC5870, June 2010,
              <http://www.rfc-editor.org/info/rfc5870>.

   [RFC5988]  Nottingham, M., "Web Linking", RFC 5988,
              DOI 10.17487/RFC5988, October 2010,
              <http://www.rfc-editor.org/info/rfc5988>.

   [RFC6047]  Melnikov, A., Ed., "iCalendar Message-Based
              Interoperability Protocol (iMIP)", RFC 6047,
              DOI 10.17487/RFC6047, December 2010,
              <http://www.rfc-editor.org/info/rfc6047>.

   [RFC6901]  Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed.,
              "JavaScript Object Notation (JSON) Pointer", RFC 6901,
              DOI 10.17487/RFC6901, April 2013,
              <http://www.rfc-editor.org/info/rfc6901>.

   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <http://www.rfc-editor.org/info/rfc7159>.

   [RFC7265]  Kewisch, P., Daboo, C., and M. Douglass, "jCal: The JSON
              Format for iCalendar", RFC 7265, DOI 10.17487/RFC7265, May
              2014, <http://www.rfc-editor.org/info/rfc7265>.

   [RFC7493]  Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
              DOI 10.17487/RFC7493, March 2015,
              <http://www.rfc-editor.org/info/rfc7493>.

   [RFC7529]  Daboo, C. and G. Yakushev, "Non-Gregorian Recurrence Rules
              in the Internet Calendaring and Scheduling Core Object
              Specification (iCalendar)", RFC 7529,
              DOI 10.17487/RFC7529, May 2015,
              <http://www.rfc-editor.org/info/rfc7529>.






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   [RFC7986]  Daboo, C., "New Properties for iCalendar", RFC 7986,
              DOI 10.17487/RFC7986, October 2016,
              <http://www.rfc-editor.org/info/rfc7986>.

10.2.  Informative References

   [draft-apthorp-ical-tasks]
              "Task Extensions to iCalendar",
              <https://tools.ietf.org/html/draft-apthorp-ical-tasks>.

   [draft-daboo-valarm-extensions]
              "VALARM Extensions for iCalendar",
              <https://tools.ietf.org/html/draft-daboo-valarm-
              extensions>.

   [draft-ietf-calext-ical-relations]
              "Support for iCalendar Relationships",
              <https://tools.ietf.org/html/draft-ietf-calext-ical-
              relations>.

10.3.  URIs

   [1] https://www.w3.org/TR/2011/REC-css3-color-20110607/#svg-color

   [2] http://www.iana.org/time-zones

Authors' Addresses

   Neil Jenkins
   FastMail
   PO Box 234
   Collins St West
   Melbourne  VIC 8007
   Australia

   Email: neilj@fastmailteam.com
   URI:   https://www.fastmail.com


   Robert Stepanek
   FastMail
   PO Box 234
   Collins St West
   Melbourne  VIC 8007
   Australia

   Email: rsto@fastmailteam.com
   URI:   https://www.fastmail.com



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