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


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/.

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

Copyright Notice

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Table of Contents

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 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:

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 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:

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:

    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:

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 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:

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.

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 without a start recurs by its due date/time, if defined.

A Recurrence object has the following properties:

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:

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:

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:

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 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:

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. 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:

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:

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 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.

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:

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:

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:

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 property value MUST be event.

In addition to the common JSCalendar object properties 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 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).

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:

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 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 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 as JSTask has the following properties:

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. 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 instance. Also see the definition of the relatedTo 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:

4.3. JSGroup

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

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

Its @type property value MUST be group.

JSGroup supports the following JSCalendar properties:

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.

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".

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].

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].

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: 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.

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.

        "@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.

      "@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."

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.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002.
[RFC5545] Desruisseaux, B., "Internet Calendaring and Scheduling Core Object Specification (iCalendar)", RFC 5545, DOI 10.17487/RFC5545, September 2009.
[RFC5546] Daboo, C., "iCalendar Transport-Independent Interoperability Protocol (iTIP)", RFC 5546, DOI 10.17487/RFC5546, December 2009.
[RFC5646] Phillips, A. and M. Davis, "Tags for Identifying Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646, September 2009.
[RFC5870] Mayrhofer, A. and C. Spanring, "A Uniform Resource Identifier for Geographic Locations ('geo' URI)", RFC 5870, DOI 10.17487/RFC5870, June 2010.
[RFC5988] Nottingham, M., "Web Linking", RFC 5988, DOI 10.17487/RFC5988, October 2010.
[RFC6047] Melnikov, A., "iCalendar Message-Based Interoperability Protocol (iMIP)", RFC 6047, DOI 10.17487/RFC6047, December 2010.
[RFC6901] Bryan, P., Zyp, K. and M. Nottingham, "JavaScript Object Notation (JSON) Pointer", RFC 6901, DOI 10.17487/RFC6901, April 2013.
[RFC7159] Bray, T., "The JavaScript Object Notation (JSON) Data Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 2014.
[RFC7265] Kewisch, P., Daboo, C. and M. Douglass, "jCal: The JSON Format for iCalendar", RFC 7265, DOI 10.17487/RFC7265, May 2014.
[RFC7493] Bray, T., "The I-JSON Message Format", RFC 7493, DOI 10.17487/RFC7493, March 2015.
[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.
[RFC7986] Daboo, C., "New Properties for iCalendar", RFC 7986, DOI 10.17487/RFC7986, October 2016.

10.2. Informative References

[draft-apthorp-ical-tasks] "Task Extensions to iCalendar"
[draft-daboo-valarm-extensions] "VALARM Extensions for iCalendar"
[draft-ietf-calext-ical-relations] "Support for iCalendar Relationships"

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