Calendaring extensions N. Jenkins
Internet-Draft R. Stepanek
Intended status: Standards Track Fastmail
Expires: February 20, 2021 August 19, 2020

JSCalendar: A JSON representation of calendar data
draft-ietf-calext-jscalendar-29

Abstract

This specification defines a data model and 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 and, over time, successor to the widely deployed iCalendar data format, and to be unambiguous, extendable, and simple to process. In contrast to the jCal format, which is also JSON-based, JSCalendar is not a direct mapping from iCalendar, but defines the data model independently and expands semantics where appropriate.

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 https://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 20, 2021.

Copyright Notice

Copyright (c) 2020 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 (https://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.

Table of Contents

1. Introduction

This document defines a data model for calendar event and task objects, or groups of such objects, in electronic calendar applications and systems. The format aims to be unambiguous, extendable and simple to process.

The key design considerations for this data model are as follows:

The representation of this data model is defined in the I-JSON format [RFC7493], which is a strict subset of the JavaScript Object Notation (JSON) Data Interchange Format [RFC8259]. Using JSON is mostly a pragmatic choice: its widespread use makes JSCalendar easier to adopt, and the ready availability of production-ready JSON implementations eliminates a whole category of parser-related interoperability issues, which iCalendar has often suffered from.

1.1. Motivation and Relation to iCalendar and jCal

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 backward-incompatible changes.

Sources of implementation errors include the following:

In recent years, many new products and services have appeared that wish to use a JSON representation of calendar data within their APIs. The JSON format for iCalendar data, jCal, is a direct mapping between iCalendar and JSON. In its effort to represent full iCalendar semantics, it inherits all the same pitfalls and uses a complicated JSON structure.

As a consequence, since the standardization of jCal, the majority of implementations and service providers either kept using iCalendar, or came up with their own proprietary JSON representations, which are incompatible with each other and often suffer from common pitfalls, such as storing event start times in UTC (which become incorrect if the timezone's rules change in the future). JSCalendar meets the demand for JSON-formatted calendar data that is free of such known problems and provides a standard representation as an alternative to the proprietary formats.

1.2. Notational Conventions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

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 [RFC8259].

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.

1.3. Type Signatures

Type signatures are given for all JSON values in this document. The following conventions are used:

Other types may also be given, with their representations defined elsewhere in this document.

1.4. Data Types

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

1.4.1. Int

Where Int is given as a data type, it means an integer in the range -2^53+1 <= value <= 2^53-1, the safe range for integers stored in a floating-point double, represented as a JSON Number.

1.4.2. UnsignedInt

Where UnsignedInt is given as a data type, it means an integer in the range 0 <= value <= 2^53-1, represented as a JSON Number.

1.4.3. UTCDateTime

This is a string in [RFC3339] date-time format, with the further restrictions that any letters MUST be in uppercase, the time component MUST be included and the time offset MUST be the character Z. Fractional second values MUST NOT be included unless non-zero and MUST NOT have trailing zeros, to ensure there is only a single representation for each date-time.

For example 2010-10-10T10:10:10.003Z is OK, but 2010-10-10T10:10:10.000Z is invalid and is correctly encoded as 2010-10-10T10:10:10Z.

1.4.4. LocalDateTime

This is a date-time string with no time zone/offset information. It is otherwise in the same format as UTCDateTime, including fractional seconds. For example 2006-01-02T15:04:05 and 2006-01-02T15:04:05.003 are both valid. The time zone to associate the LocalDateTime with comes from an associated property, or if no time zone is associated it defines floating time. Floating date-times are not tied to any specific time zone. Instead, they occur in each time zone at the given wall-clock time (as opposed to the same instant point in time).

A time zone may have a period of discontinuity, for example a change from standard time to daylight-savings time. When converting local date-times that fall in the discontinuity to UTC, the offset before the transition is used.

For example, in the America/Los_Angeles time zone, the date-time 2020-11-01T01:30:00 occurs twice: before the DST transition with a UTC offset of -07:00, and again after the transition with an offset of -08:00. When converting to UTC, we therefore use the offset before the transition (-07:00) and so it becomes 2020-11-01T08:30:00Z.

Similarly, in the Australia/Melbourne time zone, the date-time 2020-10-04T02:30:00 does not exist: the clocks are moved forward one hour for DST on that day at 02:00. However, such a value may appear during calculations (see duration semantics below), or due to a change in time zone rules (so it was valid when the event was first created). Again, it is interpreted as though the offset before the transition is in effect (+10:00), therefore when converted to UTC we get 2020-10-03T16:30:00Z.

1.4.5. Duration

Where Duration is given as a type, it means a length of time represented by a subset of ISO8601 duration format, as specified by the following ABNF [RFC5234]:

    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"
    dur-week    = 1*DIGIT "W"
    dur-cal     = (dur-week [dur-day] / dur-day)

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

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

A duration specifies an abstract number of weeks, days, hours, minutes, and/or seconds. A duration specified using weeks or days does not always correspond to an exact multiple of 24 hours. The number of hours/minutes/seconds may vary if it overlaps a period of discontinuity in the event's time zone, for example a change from standard time to daylight-savings time. Leap seconds MUST NOT be considered when adding or subtracting a duration to/from a LocalDateTime.

To add a duration to a LocalDateTime:

  1. Add any week or day components of the duration to the date.
  2. If a time zone applies to the LocalDateTime, convert it to a UTCDateTime following the semantics in Section 1.4.4.
  3. Add any hour, minute or second components of the duration (in absolute time).
  4. Convert the resulting UTCDateTime back to a LocalDateTime in the time zone that applies.

To subtract a duration from a LocalDateTime, the steps apply in reverse:

  1. If a time zone applies to the LocalDateTime, convert it to UTC following the semantics in Section 1.4.4.
  2. Subtract any hour, minute or second components of the duration (in absolute time).
  3. Convert the resulting UTCDateTime back to LocalDateTime in the time zone that applies.
  4. Subtract any week or day components of the duration from the date.
  5. If the resulting time does not exist on the date due to a discontinuity in the time zone, use the semantics in Section 1.4.4 to convert to UTC and back to get a valid LocalDateTime.

These semantics match the iCalendar DURATION value type ([RFC5545], Section 3.3.6).

1.4.6. SignedDuration

A SignedDuration represents a length of time that may be positive or negative and is typically used to express the offset of a point in time relative to an associated time. It is represented as a Duration, optionally preceded by a sign character. It is specified by the following ABNF:

    signed-duration = ["+" / "-"] duration

A negative sign indicates a point in time at or before the associated time, a positive or no sign a time at or after the associated time.

1.4.7. Id

Where Id is given as a data type, it means a String of at least 1 and a maximum of 255 octets in size, and it MUST only contain characters from the "URL and Filename Safe" base64url alphabet, as defined in Section 5 of [RFC4648], excluding the pad character (=). This means the allowed characters are the ASCII alphanumeric characters (A-Za-z0-9), hyphen (-), and underscore (_).

Unless otherwise specified, Ids are arbitrary and only have meaning within the object where they are being used. Ids need not be unique among different objects. For example, two JSEvent objects might use the same ids in their respective links properties. Or within the same JSEvent object the same Id could appear in the participants and alerts properties. These situations do not imply any semantic connections among the objects.

Nevertheless, a UUID is typically a good choice.

1.4.8. PatchObject

A PatchObject is of type String[*], and represents an unordered set of patches on a JSON object. Each key is a path represented in a subset of JSON pointer format [RFC6901]. The paths have an implicit leading /, so each key is prefixed with / before applying the JSON pointer evaluation algorithm.

A patch within a PatchObject is only valid if all of the following conditions apply:

  1. The pointer MUST NOT insert/delete from an array; the array MUST be replaced in its entirety instead.
  2. When evaluating a path, all parts prior to the last (i.e., the value after the final slash) MUST exist.
  3. There MUST NOT be two patches in the PatchObject where the pointer of one is a prefix of the pointer of the other, e.g., alerts/foo/offset and alerts.
  4. The value for the patch MUST be valid for the property being set (of the correct type and obeying any other applicable restrictions), or if null the property MUST be optional.

The value associated with each pointer is either:

A PatchObject does not define its own @type property. A @type property in a patch MUST be handled as any other patched property value.

Implementations MUST reject in its entirety a PatchObject if any of its patches is invalid. Implementations MUST NOT apply partial patches.

1.4.9. Time Zones

By default, time zones in JSCalendar are identified by their names in the IANA Time Zone Database [TZDB], and the zone rules of the respective zone records apply.

Implementations MAY embed the definitions of custom time zones in the timeZones property (see Section 4.7.2).

1.4.10. Relation

A Relation object defines the relation to other objects, using a possibly empty set of relation types. The object that defines this relation is the linking object, while the other object is the linked object. The Relation object has the following properties:

2. JSCalendar Objects

This section describes the calendar object types specified by JSCalendar.

2.1. JSEvent

Media type: application/jscalendar+json;type=jsevent

A JSEvent represents a scheduled amount of time on a calendar, typically a meeting, appointment, reminder or anniversary. It is required to start at a certain point in time and typically has a non-zero duration. Multiple participants may partake in the event at multiple locations.

The @type property value MUST be jsevent.

2.2. JSTask

Media type: application/jscalendar+json;type=jstask

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

The @type property value MUST be jstask.

2.3. JSGroup

Media type: application/jscalendar+json;type=jsgroup

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

The @type property value MUST be jsgroup.

3. 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 [RFC8259]. Property names and values are case-sensitive.

The object has a collection of properties, as specified in the following sections. Properties are specified as being either mandatory or optional. Optional properties may have a default value, if explicitly specified in the property definition.

3.1. Object Type

JSCalendar objects MUST name their type in the @type property, if not explicitly specified otherwise for the respective object type. A notable exception to this rule is the PatchObject.

3.2. Normalization and Equivalence

JSCalendar aims to provide unambiguous definitions for value types and properties, but does not define a general normalization or equivalence method for JSCalendar objects and types. This is because the notion of equivalence might range from byte-level equivalence to semantic equivalence, depending on the respective use case.

Normalization of JSCalendar objects is hindered because of the following reasons:

Considering this, the definition of equivalence and normalization is left to client and server implementations and to be negotiated by a calendar exchange protocol or defined elsewhere.

3.3. Vendor-specific Property Extensions, Values and Types

Vendors MAY add additional properties to the calendar object to support their custom features. To avoid conflict, the names of these properties MUST be prefixed by a domain name controlled by the vendor followed by a colon, e.g., example.com:customprop. If the value is a new JSCalendar object, it either MUST include a @type property or it MUST explicitly be specified to not require a type designator. The type name MUST be prefixed with a domain name controlled by the vendor.

Some JSCalendar properties allow vendor-specific value extensions. Such vendor-specific values MUST be prefixed by a domain name controlled by the vendor followed by a colon, e.g., example.com:customrel.

Vendors are strongly encouraged to register any new property values or extensions that are useful to other systems as well, rather than use a vendor-specific prefix.

4. Common JSCalendar Properties

This section describes the properties that are common to the various JSCalendar object types. Specific JSCalendar object types may only support a subset of these properties. The object type definitions in Section 5 describe the set of supported properties per type.

4.1. Metadata Properties

4.1.1. @type

Type: String (mandatory).

Specifies the type which this object represents. This MUST be one of the following values:

4.1.2. uid

Type: String (mandatory).

A globally unique identifier, used to associate the object as the same across different systems, calendars and views. The value of this property MUST be unique across all JSCalendar objects, even if they are of different type. [RFC4122] describes a range of established algorithms to generate universally unique identifiers (UUID). UUID version 4, described in Section 4.4 of [RFC4122], is RECOMMENDED.

For compatibility with [RFC5545] UIDs, implementations MUST be able to receive and persist values of at least 255 octets for this property, but they MUST NOT truncate values in the middle of a UTF-8 multi-octet sequence.

4.1.3. relatedTo

Type: String[Relation] (optional).

Relates the object to other JSCalendar objects. This is represented as a map of the UIDs of the related objects to information about the relation.

If an object is split to make a "this and future" change to a recurrence, the original object MUST be truncated to end at the previous occurrence before this split, and a new object created to represent all the occurrences after the split. A next relation MUST be set on the original object's relatedTo property for the UID of the new object. A first relation for the UID of the first object in the series MUST 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.

4.1.4. prodId

Type: String (optional).

The identifier for the product that last updated the JSCalendar object. This should be set whenever the data in the object is modified (i.e., whenever the "updated" property is set).

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]. It MUST only use characters of an iCalendar TEXT data value (see Section 3.3.11 of [RFC5545]).

This property SHOULD NOT be used to alter the interpretation of a 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, a practice that is knows to cause long-term interoperability problems.

4.1.5. created

Type: UTCDateTime (optional).

The date and time this object was initially created.

4.1.6. updated

Type: UTCDateTime (mandatory).

The date and time the data in this object was last modified (or its creation date/time if not modified since).

4.1.7. sequence

Type: UnsignedInt (optional, default: 0).

Initially zero, this MUST be incremented by one every time a change is made to the object, except if the change only modifies the participants property (see Section 4.4.5).

This is used as part of iTIP [RFC5546] to know which version of the object a scheduling message relates to.

4.1.8. method

Type: String (optional).

The iTIP [RFC5546] method, in lowercase. This MUST only be present if the JSCalendar object represents an iTIP scheduling message.

4.2. What and Where Properties

4.2.1. title

Type: String (optional, default: empty String).

A short summary of the object.

4.2.2. description

Type: String (optional, default: empty String).

A longer-form text description of the object. The content is formatted according to the descriptionContentType property.

4.2.3. descriptionContentType

Type: String (optional, default: text/plain).

Describes the media type [RFC6838] of the contents of the description property. Media types MUST be sub-types of type text, and SHOULD be text/plain or text/html [MIME]. They MAY include parameters and the charset parameter value MUST be utf-8, if specified. Descriptions of type text/html MAY contain cid URLs [RFC2392] to reference links in the calendar object by use of the cid property of the Link object.

4.2.4. showWithoutTime

Type: Boolean (optional, default: false).

Indicates that the time is not important to display to the user when rendering this calendar object. An example of this is an event that conceptually occurs all day or across multiple days, such as "New Year's Day" or "Italy Vacation". While the time component is important for free-busy calculations and checking for scheduling clashes, calendars may choose to omit displaying it and/or display the object separately to other objects to enhance the user's view of their schedule.

Such events are also commonly known as "all-day" events.

4.2.5. locations

Type: Id[Location] (optional).

A map of location ids to Location objects, representing locations associated with the object.

A Location object has the following properties. It MUST have at least one property other than the relativeTo property.

4.2.6. virtualLocations

Type: Id[VirtualLocation] (optional).

A map of ids to VirtualLocation objects, representing virtual locations, such as video conferences or chat rooms, associated with the object.

A VirtualLocation object has the following properties.

4.2.7. links

Type: Id[Link] (optional).

A map of link ids to Link objects, representing external resources associated with the object.

A Link object has the following properties:

4.2.8. locale

Type: String (optional).

The language tag as defined in [RFC5646] that best describes the locale used for the text in the calendar object, if known.

4.2.9. keywords

Type: String[Boolean] (optional).

A set of keywords or tags that relate to the object. The set is represented as a map, with the keys being the keywords. The value for each key in the map MUST be true.

4.2.10. categories

Type: String[Boolean] (optional).

A set of categories that relate to the calendar object. The set is represented as a map, with the keys being the categories specified as URIs. The value for each key in the map MUST be true.

In contrast to keywords, categories typically are structured. For example, a vendor owning the domain example.com might define the categories http://example.com/categories/sports/american-football and http://example.com/categories/music/r-b.

4.2.11. color

Type: String (optional).

A color clients MAY use when displaying this calendar object. The value is a color name taken from the set of names defined in Section 4.3 of CSS Color Module Level 3 [COLORS], or an RGB value in hexadecimal notation, as defined in Section 4.2.1 of CSS Color Module Level 3.

4.3. Recurrence Properties

Some events and tasks occur at regular or irregular intervals. Rather than having to copy the data for every occurrence there can be a master event with rules to generate recurrences, and/or overrides that add extra dates or exceptions to the rules.

The recurrence set is the compelete set of instances for an object. It is generated by considering the following properties in order, all of which are optional:

  1. The recurrenceRules property (Section 4.3.2) generates a set of extra date-times on which the object occurs.
  2. The excludedRecurrenceRules property (Section 4.3.3) generates a set of date-times that are to be removed from the previously generated set of date-times on which the object occurs.
  3. The recurrenceOverrides property (Section 4.3.4) defines date-times which are added or excluded to form the final set. (This property may also contain changes to the object to apply to particular instances.)

4.3.1. recurrenceId

Type: LocalDateTime (optional).

If present, this JSCalendar object represents one occurrence of a recurring JSCalendar object. If present the recurrenceRules and recurrenceOverrides properties MUST NOT be present.

The value is a date-time either produced by the recurrenceRules of the master event, or added as a key to the recurrenceOverrides property of the master event.

4.3.2. recurrenceRules

Type: RecurrenceRule[] (optional).

Defines a set of recurrence rules (repeating patterns) for recurring calendar objects.

A JSEvent recurs by applying the recurrence rules to the start date-time.

A JSTask recurs by applying the recurrence rules to the start date-time, if defined, otherwise it recurs by the due date-time, if defined. If the task defines neither a start nor due date-time, it MUST NOT define a recurrenceRules property.

If multiple recurrence rules are given, each rule is to be applied and then the union of the results used, ignoring any duplicates.

A RecurrenceRule object is a JSON object mapping of a RECUR value type in iCalendar [RFC5545] [RFC7529] and has the same semantics. It has the following properties:

4.3.2.1. Interpreting recurrence rules

A recurrence rule specifies a set of date-times for recurring calendar objects. A recurrence rule has the following semantics. Note, wherever "year", "month" or "day of month" is used, this is within the calendar system given by the "rscale" property, which defaults to "gregorian" if omitted.

  1. A set of candidates is generated. This is every second within a period defined by the frequency property value:
  2. Each date-time candidate is compared against all of the byX properties of the rule except bySetPosition. If any property in the rule does not match the date-time, it is eliminated. Each byX property is an array; the date-time matches the property if it matches any of the values in the array. The properties have the following semantics:

    If a skip property is defined and is not "omit", there may be candidates that do not correspond to valid dates (e.g., 31st February in the Gregorian calendar). In this case, the properties MUST be considered in the order above and:

    1. After applying the byMonth filter, if the candidate's month is invalid for the given year, increment it (if skip is "forward") or decrement it (if skip is "backward") until a valid month is found, incrementing/decrementing the year as well if passing through the beginning/end of the year. This only applies to calendar systems with leap months.
    2. After applying the byMonthDay filter, if the day of the month is invalid for the given month and year, change the date to the first day of the next month (if skip is "forward") or the last day of the current month (if skip is "backward").
    3. If any valid date produced after applying the skip is already a candidate, eliminate the duplicate. (For example after adjusting, 30th February and 31st February would both become the same "real" date, so one is eliminated as a duplicate.)

  3. If a bySetPosition property is included, this is now applied to the ordered list of remaining dates. This property specifies the indexes of date-times to keep; all others should be eliminated. Negative numbers are indexes from the end of the list, with -1 being the last item.
  4. Any date-times before the start date of the event are eliminated (see below for why this might be needed).
  5. If a skip property is included and is not "omit", eliminate any date-times that have already been produced by previous iterations of the algorithm. (This is not possible if skip is "omit".)
  6. If further dates are required (we have not reached the until date, or count limit) skip the next (interval - 1) sets of candidates, then continue from step 1.

When determining the set of occurrence dates for an event or task, the following extra rules must be applied:

  1. The initial date-time to which the rule is applied (the start date-time for events; the start or due date-time for tasks) is always the first occurrence in the expansion (and is counted if the recurrence is limited by a "count" property), even if it would normally not match the rule.
  2. The first set of candidates to consider is that which would contain the initial date-time. This means the first set may include candidates before the initial date-time; such candidates are eliminated from the results in step (4) as outlined before.
  3. The following properties MUST be implicitly added to the rule under the given conditions:

4.3.3. excludedRecurrenceRules

Type: RecurrenceRule[] (optional).

Defines a set of recurrence rules (repeating patterns) for date-times on which the object will not occur. The rules are interpreted the same as for the "recurrenceRules" property (see Section 4.3.2), with the exception that the initial date-time to which the rule is applied (the "start" date-time for events; the "start" or "due" date-time for tasks) is only considered part of the expansion if it matches the rule. The resulting set of date-times are then removed from those generated by the recurrenceRules property, as described in Section 4.3.

4.3.4. recurrenceOverrides

Type: LocalDateTime[PatchObject] (optional).

A map of the recurrence ids (the date-time produced by the recurrence rule) to an object of patches to apply to the generated occurrence object.

If the recurrence id does not match a date-time from the recurrence rule (or no rule is specified), it is to be treated as an additional occurrence (like an RDATE from iCalendar). The patch object may often be empty in this case.

If the patch object defines the excluded property value to be true, then the recurring calendar object does not occur at the recurrence id date-time (like an EXDATE from iCalendar). Such a patch object MUST NOT patch any other property.

By default, an occurrence inherits all properties from the main object except the start (or due) date-time, which is shifted to match the recurrence id LocalDateTime. However, individual properties of the occurrence can be modified by a patch, or multiple patches. It is valid to patch the start property value, and this patch takes precedence over the value generated from the recurrence id. Both the recurrence id as well as the patched start date-time may occur before the original JSCalendar object's start or due date.

A pointer in the PatchObject MUST be ignored if it starts with one of the following prefixes:

4.3.5. excluded

Type: Boolean (optional, default: false).

Defines if this object is an overridden, excluded instance of a recurring JSCalendar object (see Section 4.3.4). If this property value is true, this calendar object instance MUST be removed from the occurrence expansion. The absence of this property or its default value false indicates that this instance MUST be included in the occurrence expansion.

4.4. Sharing and Scheduling Properties

4.4.1. priority

Type: Int (optional, default: 0).

Specifies a priority for the calendar object. 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, for which the treatment will vary by situation. 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.

4.4.2. freeBusyStatus

Type: String (optional, default: busy).

Specifies how this calendar object should be treated when calculating free-busy state. This MUST be one of the following values, a value registered in the IANA JSCalendar Enum Registry, or a vendor-specific value:

4.4.3. privacy

Type: String (optional, default: public).

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. Enforcement of the restrictions indicated by this property are up to the API via which this object is accessed.

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 one of the following values, a value registered in the IANA JSCalendar Enum Registry, or a vendor-specific value. Any value the client or server doesn't understand should be preserved but treated as equivalent to private.

4.4.4. replyTo

Type: String[String] (optional).

Represents methods by which participants may submit their RSVP response to the organizer of the calendar object. The keys in the property value are the available methods and MUST only contain ASCII alphanumeric characters (A-Za-z0-9). The value is a URI for the method specified in the key. Future methods may be defined in future specifications and registered with IANA; a calendar client MUST ignore any method it does not understand, but MUST preserve the method key and URI. This property MUST be omitted if no method is defined (rather than being specified as an empty object).

The following methods are defined:

4.4.5. participants

Type: Id[Participant] (optional).

A map of participant ids to participants, describing their participation in the calendar object.

If this property is set and any participant has a sendTo property, then the replyTo property of this calendar object MUST define at least one reply method.

A Participant object has the following properties:

4.5. Alerts Properties

4.5.1. useDefaultAlerts

Type: Boolean (optional, default: false).

If true, use the user's default alerts and ignore the value of the alerts property. Fetching user defaults is dependent on the API from which this JSCalendar object is being fetched, and is not defined in this specification. If an implementation cannot determine the user's default alerts, or none are set, it MUST process the alerts property as if useDefaultAlerts is set to false.

4.5.2. alerts

Type: Id[Alert] (optional).

A map of alert ids to Alert objects, representing alerts/reminders to display or send to the user for this calendar object.

An Alert Object has the following properties:

4.6. Multilingual Properties

4.6.1. localizations

Type: String[PatchObject] (optional).

A map of language tags [RFC5646] to patch objects, which localize the calendar object into the locale of the respective language tag.

See the description of PatchObject for the structure of the PatchObject. The patches are applied to the top-level calendar object. In addition, the locale property of the patched object is set to the language tag. All pointers for patches MUST end with one of the following suffixes; any patch that does not follow this MUST be ignored unless otherwise specified in a future RFC: recurrenceOverrides; any localization of the override MUST be a patch to the localizations property inside the override instead. For example, a patch to locations/abcd1234/title is permissible, but a patch to uid or recurrenceOverrides/2018-01-05T14:00:00/title is not.

A patch MUST NOT have the prefix

Note that this specification does not define how to maintain validity of localized content. For example, a client application changing a JSCalendar object's title property might also need to update any localizations of this property. Client implementations SHOULD provide the means to manage localizations, but how to achieve this is specific to the application's workflow and requirements.

4.7. Time Zone Properties

4.7.1. timeZone

Type: String|null (optional, default: null).

Identifies the time zone the object is scheduled in, or null for floating time. This is either a name from the IANA Time Zone Database [TZDB] or the id of a custom time zone from the timeZones property (see Section 1.4.9). If omitted, this MUST be presumed to be null (i.e., floating time).

4.7.2. timeZones

Type: String[TimeZone] (optional).

Maps identifiers of custom time zones to their time zone definitions. The following restrictions apply for each key in the map:

An identifier need only be unique to this JSCalendar object. A JSCalendar object may be part in a hierarchy of other JSCalendar objects (say, a JSEvent is an entry in a JSGroup). In this case, the set of time zones is the sum of the time zone definitions of this object and its parent objects. If multiple time zones with the same identifier exist, then the definition closest to the calendar object in relation to its parents MUST be used. (In context of JSEvent, a time zone definition in its timeZones property has precedence over a definition of the same id in the JSGroup). Time zone definitions in any children of the calendar object MUST be ignored.

A TimeZone object maps a VTIMEZONE component from iCalendar [RFC5545] and the semantics are as defined there. A valid time zone MUST define at least one transition rule in the standard or daylight property. Its properties are:

A TimeZoneRule object maps a STANDARD or DAYLIGHT sub-component from iCalendar, with the restriction that at most one recurrence rule is allowed per rule. It has the following properties:

5. Type-specific JSCalendar Properties

5.1. JSEvent Properties

In addition to the common JSCalendar object properties a JSEvent has the following properties:

5.1.1. start

Type: LocalDateTime (mandatory).

The date/time the event starts in the event's time zone (as specified in the timeZone property, see Section 4.7.1).

5.1.2. duration

Type: Duration (optional, default: PT0S).

The zero or positive duration of the event in the event's start time zone.

A JSEvent MAY involve start and end locations that are in different time zones (e.g., a trans-continental flight). This can be expressed using the relativeTo and timeZone properties of the JSEvent's Location objects (see Section 4.2.5).

5.1.3. status

Type: String (optional, default: confirmed).

The scheduling status (Section 4.4) of a JSEvent. If set, it MUST be one of the following values, a value registered in the IANA JSCalendar Enum Registry, or a vendor-specific value:

5.2. JSTask Properties

In addition to the common JSCalendar object properties a JSTask has the following properties:

5.2.1. due

Type: LocalDateTime (optional).

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

5.2.2. start

Type: LocalDateTime (optional).

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

5.2.3. estimatedDuration

Type: Duration (optional).

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

5.2.4. percentComplete

Type: UnsignedInt (optional).

Represents the percent completion of the task overall. The property value MUST be a positive integer between 0 and 100.

5.2.5. progress

Type: String (optional).

Defines the progress of this task. If omitted, the default progress (Section 4.4) of a JSTask is defined as follows (in order of evaluation):

If set, it MUST be one of the following values, a value registered in the IANA JSCalendar Enum Registry, or a vendor-specific value:

5.2.6. progressUpdated

Type: UTCDateTime (optional).

Specifies the date/time the progress property of either the task overall (Section 5.2.5) or a specific participant (Section 4.4.5) was last updated.

If the task is recurring and has future instances, a client may want to keep track of the last progress update timestamp of a specific task recurrence, but leave other instances unchanged. One way to achieve this is by overriding the progressUpdated property in the task recurrenceOverrides property. However, this could produce a long list of timestamps for regularly recurring tasks. An alternative approach is to split the JSTask into a current, single instance of JSTask with this instance progress update time and a future recurring instance. See also Section 4.1.3 on splitting.

5.3. JSGroup Properties

JSGroup supports the following common JSCalendar properties:

In addition, the following JSGroup-specific properties are supported:

5.3.1. entries

Type: (JSTask|JSEvent)[] (mandatory).

A collection of group members. Implementations MUST ignore entries of unknown type.

5.3.2. source

Type: String (optional).

The source from which updated versions of this group may be retrieved from. The value MUST be a URI.

6. Examples

The following examples illustrate several aspects of the JSCalendar data model and format. The examples may omit mandatory or additional properties, which is indicated by a placeholder property with key .... While most of the examples use calendar event objects, they are also illustrative for tasks.

6.1. Simple event

This example illustrates a simple one-time event. It specifies a one-time event that begins on January 15, 2018 at 1pm New York local time and ends after 1 hour. 

{
  "@type": "jsevent",
  "uid": "2a358cee-6489-4f14-a57f-c104db4dc2f1",
  "updated": "2018-01-15T18:00:00Z",
  "title": "Some event",
  "start": "2018-01-15T13:00:00",
  "timeZone": "America/New_York",
  "duration": "PT1H"
}

6.2. Simple task

This example illustrates a simple task for a plain to-do item. 

{
  "@type": "jstask",
  "uid": "2a358cee-6489-4f14-a57f-c104db4dc2f2",
  "updated": "2018-01-15T18:00:00Z",
  "title": "Do something"
}

6.3. Simple group

This example illustrates a simple calendar object group that contains an event and a task. 

{
  "@type": "jsgroup",
  "uid": "2a358cee-6489-4f14-a57f-c104db4dc343",
  "updated": "2018-01-15T18:00:00Z",
  "name": "A simple group",
  "entries": [{
    "@type": "jsevent",
    "uid": "2a358cee-6489-4f14-a57f-c104db4dc2f1",
    "updated": "2018-01-15T18:00:00Z",
    "title": "Some event",
    "start": "2018-01-15T13:00:00",
    "timeZone": "America/New_York",
    "duration": "PT1H"
  },
  "2a358cee-6489-4f14-a57f-c104db4dc2f2": {
    "@type": "jstask",
    "uid": "2a358cee-6489-4f14-a57f-c104db4dc2f2",
    "updated": "2018-01-15T18:00:00Z",
    "title": "Do something"
  }]
}

6.4. All-day event

This example illustrates an event for an international holiday. It specifies an all-day event on April 1 that occurs every year since the year 1900. 

{
  "...": "",
  "title": "April Fool's Day",
  "showWithoutTime": true,
  "start": "1900-04-01T00:00:00",
  "duration": "P1D",
  "recurrenceRules": [{
    "@type": "RecurrenceRule",
    "frequency": "yearly"
  }]
}

6.5. Task with a due date

This example illustrates a task with a due date. It is a reminder to buy groceries before 6pm Vienna local time on January 19, 2018. The calendar user expects to need 1 hour for shopping. 

{
  "...": "",
  "title": "Buy groceries",
  "due": "2018-01-19T18:00:00",
  "timeZone": "Europe/Vienna",
  "estimatedDuration": "PT1H"
}

6.6. Event with end time zone

This example illustrates the use of end time zones by use of an international flight. The flight starts on April 1, 2018 at 9am in Berlin local time. The duration of the flight is scheduled at 10 hours 30 minutes. The time at the flight's destination is in the same time zone as Tokyo. Calendar clients could use the end time zone to display the arrival time in Tokyo local time and highlight the time zone difference of the flight. The location names can serve as input for navigation systems. 

{
  "...": "",
  "title": "Flight XY51 to Tokyo",
  "start": "2018-04-01T09:00:00",
  "timeZone": "Europe/Berlin",
  "duration": "PT10H30M",
  "locations": {
    "2a358cee-6489-4f14-a57f-c104db4dc2f1": {
      "@type": "Location",
      "rel": "start",
      "name": "Frankfurt Airport (FRA)"
    },
    "c2c7ac67-dc13-411e-a7d4-0780fb61fb08": {
      "@type": "Location",
      "rel": "end",
      "name": "Narita International Airport (NRT)",
      "timeZone": "Asia/Tokyo"
    }
  }
}

6.7. Floating-time event (with recurrence)

This example illustrates the use of floating time. Since January 1, 2018, a calendar user blocks 30 minutes every day to practice Yoga at 7am local time, in whatever time zone the user is located on that date. 

{
  "...": "",
  "title": "Yoga",
  "start": "2018-01-01T07:00:00",
  "duration": "PT30M",
  "recurrenceRules": [{
    "@type": "RecurrenceRule",
    "frequency": "daily"
  }]
}

6.8. Event with multiple locations and localization

This example illustrates an event that happens at both a physical and a virtual location. Fans can see a live concert on premises or online. The event title and descriptions are localized. 

{
  "...": "",
  "title": "Live from Music Bowl: The Band",
  "description": "Go see the biggest music event ever!",
  "locale": "en",
  "start": "2018-07-04T17:00:00",
  "timeZone": "America/New_York",
  "duration": "PT3H",
  "locations": {
    "c0503d30-8c50-4372-87b5-7657e8e0fedd": {
      "@type": "Location",
      "name": "The Music Bowl",
      "description": "Music Bowl, Central Park, New York",
      "coordinates": "geo:40.7829,-73.9654"
    }
  },
  "virtualLocations": {
    "6f3696c6-1e07-47d0-9ce1-f50014b0041a": {
      "@type": "VirtualLocation",
      "name": "Free live Stream from Music Bowl",
      "uri": "https://stream.example.com/the_band_2018"
    }
  },
  "localizations": {
    "de": {
      "title": "Live von der Music Bowl: The Band!",
      "description": "Schau dir das größte Musikereignis an!",
      "virtualLocations/6f3696c6-1e07-47d0-9ce1-f50014b0041a/name":
                              "Gratis Live-Stream aus der Music Bowl"
    }
  }
}

6.9. Recurring event with overrides

This example illustrates the use of recurrence overrides. A math course at a University is held for the first time on January 8, 2018 at 9am London time and occurs every week until June 25, 2018. Each lecture lasts for one hour and 30 minutes and is located at the Mathematics department. This event has exceptional occurrences: at the last occurrence of the course is an exam, which lasts for 2 hours and starts at 10am. Also, the location of the exam differs from the usual location. On April 2 no course is held. On January 5 at 2pm is an optional introduction course, that occurs before the first regular lecture. 

{
  "...": "",
  "title": "Calculus I",
  "start": "2018-01-08T09:00:00",
  "timeZone": "Europe/London",
  "duration": "PT1H30M",
  "locations": {
    "2a358cee-6489-4f14-a57f-c104db4dc2f1": {
      "@type": "Location",
      "title": "Math lab room 1",
      "description": "Math Lab I, Department of Mathematics"
    }
  },
  "recurrenceRules": [{
    "@type": "RecurrenceRule",
    "frequency": "weekly",
    "until": "2018-06-25T09:00:00"
  }],
  "recurrenceOverrides": {
    "2018-01-05T14:00:00": {
      "title": "Introduction to Calculus I (optional)"
    },
    "2018-04-02T09:00:00": {
      "excluded": "true"
    },
    "2018-06-25T09:00:00": {
      "title": "Calculus I Exam",
      "start": "2018-06-25T10:00:00",
      "duration": "PT2H",
      "locations": {
        "2a358cee-6489-4f14-a57f-c104db4dc2f1": {
          "@type": "Location",
          "title": "Big Auditorium",
          "description": "Big Auditorium, Other Road"
        }
      }
    }
  }
}

6.10. Recurring event with participants

This example illustrates scheduled events. A team meeting occurs every week since January 8, 2018 at 9am Johannesburg time. The event owner also chairs the event. Participants meet in a virtual meeting room. An attendee has accepted the invitation, but on March 8, 2018 he is unavailable and declined participation for this occurrence. 

{
  "...": "",
  "title": "FooBar team meeting",
  "start": "2018-01-08T09:00:00",
  "timeZone": "Africa/Johannesburg",
  "duration": "PT1H",
  "virtualLocations": {
    "2a358cee-6489-4f14-a57f-c104db4dc2f1": {
      "@type": "VirtualLocation",
      "name": "ChatMe meeting room",
      "uri": "https://chatme.example.com?id=1234567"
    }
  },
  "recurrenceRules": [{
    "@type": "RecurrenceRule",
    "frequency": "weekly"
  }],
  "replyTo": {
    "imip": "mailto:6489-4f14-a57f-c1@schedule.example.com"
  },
  "participants": {
    "dG9tQGZvb2Jhci5xlLmNvbQ": {
      "@type": "Participant",
      "name": "Tom Tool",
      "email": "tom@foobar.example.com",
      "sendTo": {
        "imip": "mailto:6489-4f14-a57f-c1@calendar.example.com"
      },
      "participationStatus": "accepted",
      "roles": {
        "attendee": true
      }
    },
    "em9lQGZvb2GFtcGxlLmNvbQ": {
      "@type": "Participant",
      "name": "Zoe Zelda",
      "email": "zoe@foobar.example.com",
      "sendTo": {
        "imip": "mailto:zoe@foobar.example.com"
      },
      "participationStatus": "accepted",
      "roles": {
        "owner": true,
        "attendee": true,
        "chair": true
      }
    },
    "...": ""
  },
  "recurrenceOverrides": {
    "2018-03-08T09:00:00": {
      "participants/dG9tQGZvb2Jhci5xlLmNvbQ/participationStatus":
                                                          "declined"
    }
  }
}

7. Security Considerations

Calendaring and scheduling information is very privacy-sensitive. Its transmission must be done carefully to protect it from possible threats, such as eavesdropping, replay, message insertion, deletion, modification, and man-in-the-middle attacks.

The data being stored and transmitted may be used in systems with real world consequences. For example, a home automation system may turn an alarm on and off. Or a coworking space may charge money to the organiser of an event that books one of their meeting rooms. Such systems must be careful to authenticate all data they receive to prevent them from being subverted.

This document just defines the data format; such considerations are primarily the concern of the API or method of storage and transmission of such files.

7.1. Expanding Recurrences

A recurrence rule may produce infinite occurrences of an event. Implementations MUST handle expansions carefully to prevent accidental or deliberate resource exhaustion.

Conversely, a recurrence rule may be specified that does not expand to anything. It is not always possible to tell this through static analysis of the rule, so implementations MUST be careful to avoid getting stuck in infinite loops, or otherwise exhausting resources while searching for the next occurrence.

7.2. JSON Parsing

The Security Considerations of [RFC8259] apply to the use of JSON as the data interchange format.

As for any serialization format, parsers need to thoroughly check the syntax of the supplied data. JSON uses opening and closing tags for several types and structures, and it is possible that the end of the supplied data will be reached when scanning for a matching closing tag; this is an error condition, and implementations need to stop scanning at the end of the supplied data.

JSON also uses a string encoding with some escape sequences to encode special characters within a string. Care is needed when processing these escape sequences to ensure that they are fully formed before the special processing is triggered, with special care taken when the escape sequences appear adjacent to other (non-escaped) special characters or adjacent to the end of data (as in the previous paragraph).

If parsing JSON into a non-textual structured data format, implementations may need to allocate storage to hold JSON string elements. Since JSON does not use explicit string lengths, the risk of denial of service due to resource exhaustion is small, but implementations may still wish to place limits on the size of allocations they are willing to make in any given context, to avoid untrusted data causing excessive memory allocation.

7.3. URI Values

Several JSCalendar properties contain URIs as values, and processing these properties requires extra care. Section 7 of [RFC3986] discusses security risks related to URIs.

A maliciously constructed JSCalendar object may contain a very large number of URIs. In the case of published calendars with a large number of subscribers, such objects could be widely distributed. Implementations should be careful to limit the automatic fetching of linked resources to reduce the risk of this being an amplification vector for a denial-of-service attack.

7.4. Spam

Calendar systems may receive JSCalendar files from untrusted sources, in particular as attachments to emails. This can be a vector for an attacker to inject spam into a user's calendar. This may confuse, annoy, and mislead users, or overwhelm their calendar with bogus events, preventing them from seeing legitimate ones.

Heuristic, statistical or machine-learning-based filters can be effective in filtering out spam. Authentication mechanisms such as DKIM [RFC6376] can help establish the source of messages and associate the data with existing relationships (such as an address book contact). Misclassifications are always possible however, and providing a feedback mechanism for users to quickly correct this is advised.

7.5. Duplication

It is important for calendar systems to maintain the UID of an event when updating it to avoid unexpected duplication of events. When the UID changes, consumers of the data may not remove the previous version of the event if it has a different UID. This can lead to a confusing situation for the user, with many variations of the event and no indication of which one is correct. Care must be taken by consumers of the data to remove old events where possible to avoid an accidental denial-of-service attack due to the volume of data.

7.6. Time Zones

Events recur in a particular time zone. When this differs from the user's current time zone, it may unexpectedly cause an occurrence to shift in time for that user due to a daylight savings change in the event's time zone. A maliciously crafted event could attempt to confuse users with such an event to ensure a meeting is missed.

8. IANA Considerations

8.1. Media Type Registration

This document defines a media type for use with JSCalendar data formatted in JSON.

Type name:
application
Subtype name:
jscalendar+json
Required parameters:
type

The type parameter conveys the type of the JSCalendar data in the body part, with the value being one of jsevent, jstask, or jsgroup. The parameter MUST NOT occur more than once. It MUST match the value of the @type property of the JSON-formatted JSCalendar object in the body.
Optional parameters:
none
Encoding considerations:
Same as encoding considerations of application/json as specified in RFC8529, Section 11.
Security considerations:
See Section 7 of this document.
Interoperability considerations:
This media type provides an alternative to iCalendar, jCal and proprietary JSON-based calendaring data formats.
Published specification:
This specification.
Applications that use this media type:
Applications that currently make use of the text/calendar and application/calendar+json media types can use this as an alternative. Similarly, applications that use the application/json media type to transfer calendaring data can use this to further specify the content.
Fragment identifier considerations:
N/A
Additional information:
Magic number(s):
N/A
File extensions(s):
N/A
Macintosh file type code(s):
N/A

Person & email address to contact for further information:
calsify@ietf.org
Intended usage:
COMMON
Restrictions on usage:
N/A
Author:
See the "Author's Address" section of this document.
Change controller:
IETF

8.2. Creation of "JSCalendar Properties" Registry

The IANA will create the "JSCalendar Properties" registry to allow interoperability of extensions to JSCalendar objects.

This registry follows the Expert Review process ([RFC8126], Section 4.5). If the "intended use" field is common, sufficient documentation is required to enable interoperability. Preliminary community review for this registry is optional but strongly encouraged.

A registration can have an intended use of common, reserved, or obsolete. The IANA will list common-use registrations prominently and separately from those with other intended use values.

A reserved registration reserves a property name without assigning semantics to avoid name collisions with future extensions or protocol use.

An obsolete registration denotes a property that is no longer expected to be added by up-to-date systems. A new property has probably been defined covering the obsolete property's semantics.

The JSCalendar property registration procedure is not a formal standards process but rather an administrative procedure intended to allow community comment and sanity checking without excessive time delay. It is designed to encourage vendors to document and register new properties they add for use cases not covered by the original standard, leading to increased interoperability.

8.2.1. Preliminary Community Review

Notice of a potential new registration SHOULD be sent to the Calext mailing list <calsify@ietf.org> for review. This mailing list is appropriate to solicit community feedback on a proposed new property.

Properties registrations must be marked with their intended use: "common", "reserved" or "obsolete".

The intent of the public posting to this list is to solicit comments and feedback on the choice of the property name, the unambiguity of the specification document, and a review of any interoperability or security considerations. The submitter may submit a revised registration proposal or abandon the registration completely at any time.

8.2.2. Submit Request to IANA

Registration requests can be sent to <iana@iana.org>.

8.2.3. Designated Expert Review

The primary concern of the designated expert (DE) is preventing name collisions and encouraging the submitter to document security and privacy considerations. For a common-use registration, the DE is expected to confirm that suitable documentation, as described in Section 4.6 of [RFC8126], is available to ensure interoperability. That documentation will usually be in an RFC, but simple definitions are likely to use a web/wiki page, and if a sentence or two is deemed sufficient it could be described in the registry itself. The DE should also verify that the property name does not conflict with work that is active or already published within the IETF. A published specification is not required for reserved or obsolete registrations.

The DE will either approve or deny the registration request and publish a notice of the decision to the Calext WG mailing list or its successor, as well as inform IANA. A denial notice must be justified by an explanation, and, in the cases where it is possible, concrete suggestions on how the request can be modified so as to become acceptable should be provided.

8.2.4. Change Procedures

Once a JSCalendar property has been published by the IANA, the change controller may request a change to its definition. The same procedure that would be appropriate for the original registration request is used to process a change request.

JSCalendar property registrations may not be deleted; properties that are no longer believed appropriate for use can be declared obsolete by a change to their "intended use" field; such properties will be clearly marked in the lists published by the IANA.

Significant changes to a JSCalendar property's definition should be requested only when there are serious omissions or errors in the published specification, as such changes may cause interoperability issues. When review is required, a change request may be denied if it renders entities that were valid under the previous definition invalid under the new definition.

The owner of a JSCalendar property may pass responsibility to another person or agency by informing the IANA; this can be done without discussion or review.

8.2.5. JSCalendar Properties Registry Template

8.2.6. Initial Contents for the JSCalendar Properties Registry

The following table lists the initial entries of the JSCalendar Properties registry. All properties are for common-use. All RFC section references are for this document. The change controller for all these properties is "IETF".

Property Name Property Type Property Context Reference or Description
@type String JSEvent, JSTask, JSGroup, AbsoluteTrigger, Alert, Link, Location, NDay, OffsetTrigger, Participant, RecurrenceRule, Relation, TimeZone, TimeZoneRule, VirtualLocation Section 4.1.1, Section 4.5.2, Section 4.2.7, Section 4.2.5, Section 4.4.5, Section 4.3.2, Section 4.1.3, Section 4.7.2, Section 4.7.2, Section 4.2.6
acknowledged UTCDateTime Alert Section 4.5.2
action String Alert Section 4.5.2
alerts Id[Alert] JSEvent, JSTask Section 4.5.2
aliases String[Boolean] TimeZone Section 4.7.2
byDay NDay[] RecurrenceRule Section 4.3.2
byHour UnsignedInt[] RecurrenceRule Section 4.3.2
byMinute UnsignedInt[] RecurrenceRule Section 4.3.2
byMonth String[] RecurrenceRule Section 4.3.2
byMonthDay Int[] RecurrenceRule Section 4.3.2
bySecond UnsignedInt[] RecurrenceRule Section 4.3.2
bySetPosition Int[] RecurrenceRule Section 4.3.2
byWeekNo Int[] RecurrenceRule Section 4.3.2
byYearDay Int[] RecurrenceRule Section 4.3.2
categories String[Boolean] JSEvent, JSTask, JSGroup Section 4.2.10
cid String Link Section 4.2.7
color String JSEvent, JSTask, JSGroup Section 4.2.11
comments String[] TimeZoneRule Section 4.7.2
contentType String Link Section 4.2.7
coordinates String Location Section 4.2.5
count UnsignedInt RecurrenceRule Section 4.3.2
created UTCDateTime JSEvent, JSTask, JSGroup Section 4.1.5
day String NDay Section 4.3.2
daylight TimeZoneRule TimeZone Section 4.7.2
delegatedFrom String[Boolean] Participant Section 4.4.5
delegatedTo String[Boolean] Participant Section 4.4.5
description String JSEvent, JSTask, Location, Participant, VirtualLocation Section 4.2.2, Section 4.2.5, Section 4.4.5, Section 4.2.6
descriptionContentType String JSEvent, JSTask Section 4.2.3
display String Link Section 4.2.7
due LocalDateTime JSTask Section 5.2.1
duration Duration JSEvent Section 5.1.2
email String Participant Section 4.4.5
entries (JSTask|JSEvent)[] JSGroup Section 5.3.1
estimatedDuration Duration JSTask Section 5.2.3
excluded Boolean JSEvent, JSTask Section 4.3.5
excludedRecurrenceRules RecurrenceRule[] JSEvent, JSTask Section 4.3.3
expectReply Boolean Participant Section 4.4.5
firstDayOfWeek String RecurrenceRule Section 4.3.2
freeBusyStatus String JSEvent, JSTask Section 4.4.2
frequency String RecurrenceRule Section 4.3.2
href String Link Section 4.2.7
interval UnsignedInt RecurrenceRule Section 4.3.2
invitedBy String Participant Section 4.4.5
keywords String[Boolean] JSEvent, JSTask, JSGroup Section 4.2.9
kind String Participant Section 4.4.5
language String Participant Section 4.4.5
linkIds Id[Boolean] Location, Participant Section 4.2.5, Section 4.4.5
links Id[Link] JSGroup, JSEvent, JSTask Section 4.2.7
locale String JSGroup, JSEvent, JSTask Section 4.2.7
localizations String[PatchObject] JSEvent, JSTask Section 4.6.1
locationId String Participant Section 4.4.5
locations Id[Location] JSEvent, JSTask Section 4.2.5
locationTypes String[Boolean] Location Section 4.2.5
memberOf String[Boolean] Participant Section 4.4.5
method String JSEvent, JSTask Section 4.1.8
name String Location, VirtualLocation, Participant Section 4.2.5, Section 4.2.6, Section 4.4.5
names String[Boolean] TimeZoneRule Section 4.7.2
nthOfPeriod Int NDay Section 4.3.2
offset SignedDuration OffsetTrigger Section 4.5.2
offsetFrom UTCDateTime TimeZoneRule Section 4.7.2
offsetTo UTCDateTime TimeZoneRule Section 4.7.2
participants Id[Participant] JSEvent, JSTask Section 4.4.5
participationComment String Participant Section 4.4.5
participationStatus String Participant Section 4.4.5
percentComplete UnsignedInt JSTask, Participant Section 5.2.4
priority Int JSEvent, JSTask Section 4.4.1
privacy String JSEvent, JSTask Section 4.4.3
prodId String JSEvent, JSTask, JSGroup Section 4.1.4
progress String JSTask, Participant Section 5.2.5
progressUpdated UTCDateTime JSTask, Participant Section 5.2.6
recurrenceId LocalDateTime JSEvent, JSTask Section 4.3.1
recurrenceOverrides LocalDateTime[PatchObject] JSEvent, JSTask, TimeZoneRule Section 4.3.4, Section 4.7.2
recurrenceRules RecurrenceRule[] JSEvent, JSTask, TimeZoneRule Section 4.3.2, Section 4.7.2
rel String Link Section 4.2.7
relatedTo String[Relation] JSEvent, JSTask, Alert Section 4.1.3, Section 4.5.2
relation String[Boolean] Relation Section 1.4.10
relativeTo String OffsetTrigger, Location Section 4.5.2, Section 4.2.5
replyTo String[String] JSEvent, JSTask Section 4.4.4
roles String[Boolean] Participant Section 4.4.5
rscale String RecurrenceRule Section 4.3.2
standard TimeZoneRule TimeZone Section 4.7.2
start LocalDateTime TimeZoneRule Section 4.7.2
scheduleAgent String Participant Section 4.4.5
scheduleForceSend Boolean Participant Section 4.4.5
scheduleSequence UnsignedInt Participant Section 4.4.5
scheduleStatus String[] Participant Section 4.4.5
scheduleUpdated UTCDateTime Participant Section 4.4.5
sendTo String[String] Participant Section 4.4.5
sequence UnsignedInt JSEvent, JSTask Section 4.1.7
showWithoutTime Boolean JSEvent, JSTask Section 4.2.4
size UnsignedInt Link Section 4.2.7
skip String RecurrenceRule Section 4.3.2
source String JSGroup Section 5.3.2
start LocalDateTime JSEvent, JSTask Section 5.1.1, Section 5.2.2
status String JSEvent Section 5.1.3
timeZone String|null JSEvent, JSTask, Location Section 4.7.1, Section 4.2.5
timeZones String[TimeZone] JSEvent, JSTask Section 4.7.2
title String JSEvent, JSTask, JSGroup, Link Section 4.2.1
trigger OffsetTrigger|AbsoluteTrigger|UnknownTrigger Alert Section 4.5.2
tzId String TimeZone Section 4.7.2
tzUrl String TimeZone Section 4.7.2
uid String JSEvent, JSTask, JSGroup Section 4.1.2
until LocalDateTime RecurrenceRule Section 4.3.2
updated UTCDateTime JSEvent, JSTask, JSGroup Section 4.1.6
uri String VirtualLocation Section 4.2.6
useDefaultAlerts Boolean JSEvent, JSTask Section 4.5.1
validUntil UTCDateTime TimeZone Section 4.7.2
virtualLocations Id[VirtualLocation] JSEvent, JSTask Section 4.2.6
when UTCDateTime AbsoluteTrigger Section 4.5.2

8.3. Creation of "JSCalendar Types" Registry

The IANA will create the "JSCalendar Types" registry to avoid name collisions and provide a complete reference for all data types used for JSCalendar property values. The registration process is the same as for the JSCalendar Properties registry, as defined in Section 8.2.

8.3.1. JSCalendar Types Registry Template

8.3.2. Initial Contents for the JSCalendar Types Registry

The following table lists the initial entries of the JSCalendar Types registry. All properties are for common-use. All RFC section references are for this document. The change controller for all these properties is "IETF".

Type Name Reference or Description
Alert Section 4.5.2
Boolean Section 1.3
Duration Section 1.4.5
Id Section 1.4.7
Int Section 1.4.1
LocalDateTime Section 1.4.4
Link Section 4.2.7
Location Section 4.2.5
NDay Section 4.3.2
Number Section 1.3
Participant Section 4.4.5
PatchObject Section 1.4.8
RecurrenceRule Section 4.3.2
Relation Section 1.4.10
SignedDuration Section 1.4.6
String Section 1.3
TimeZone Section 4.7.2
TimeZoneRule Section 4.7.2
UnsignedInt Section 1.4.2
UTCDateTime Section 1.4.3
VirtualLocation Section 4.2.6

8.4. Creation of "JSCalendar Enum Values" Registry

The IANA will create the "JSCalendar Enum Values" registry to allow interoperable extension of semantics for properties with enumerable values. Each such property will have a subregistry of allowed values. The registration process for a new enum value or adding a new enumerable property is the same as for the JSCalendar Properties registry, as defined in Section 8.2.

8.4.1. JSCalendar Enum Property Template

This template is for adding a subregistry for a new enumerable property to the JSCalendar Enum registry.

8.4.2. JSCalendar Enum Value Template

This template is for adding a new enum value to a subregistry in the JSCalendar Enum registry.

8.4.3. Initial Contents for the JSCalendar Enum Registry

For each subregistry created in this section, all RFC section references are for this document and the change controller is IETF.

------------------------------------------------------------

Enum Values for action (Context: Alert)

Enum Value Reference or Description
display Section 4.5.2
email Section 4.5.2

------------------------------------------------------------

Enum Values for display (Context: Link)

Enum Value Reference or Description
badge Section 4.2.7
graphic Section 4.2.7
fullsize Section 4.2.7
thumbnail Section 4.2.7

------------------------------------------------------------

Enum Values for freeBusyStatus (Context: JSEvent, JSTask)

Enum Value Reference or Description
free Section 4.4.2
busy Section 4.4.2

------------------------------------------------------------

Enum Values for kind (Context: Participant)

Enum Value Reference or Description
individual Section 4.4.5
group Section 4.4.5
resource Section 4.4.5
location Section 4.4.5

------------------------------------------------------------

Enum Values for participationStatus (Context: Participant)

Enum Value Reference or Description
needs-action Section 4.4.5
accepted Section 4.4.5
declined Section 4.4.5
tenative Section 4.4.5
delegated Section 4.4.5

------------------------------------------------------------

Enum Values for privacy (Context: JSEvent, JSTask)

Enum Value Reference or Description
public Section 4.4.3
private Section 4.4.3
secret Section 4.4.3

------------------------------------------------------------

Enum Values for progress (Context: JSTask, Participant)

Enum Value Reference or Description
needs-action Section 5.2.5
in-process Section 5.2.5
completed Section 5.2.5
failed Section 5.2.5
cancelled Section 5.2.5

------------------------------------------------------------

Enum Values for relation (Context: Relation)

Enum Value Reference or Description
first Section 1.4.10
next Section 1.4.10
child Section 1.4.10
parent Section 1.4.10

------------------------------------------------------------

Enum Values for relativeTo (Context: OffsetTrigger, Location)

Enum Value Reference or Description
start Section 4.5.2
end Section 4.5.2

------------------------------------------------------------

Enum Values for roles (Context: Participant)

Enum Value Reference or Description
owner Section 4.4.5
attendee Section 4.4.5
optional Section 4.4.5
informational Section 4.4.5
chair Section 4.4.5
contact Section 4.4.5

------------------------------------------------------------

Enum Values for scheduleAgent (Context: Participant)

Enum Value Reference or Description
server Section 4.4.5
client Section 4.4.5
none Section 4.4.5

------------------------------------------------------------

Enum Values for status (Context: JSEvent)

Enum Value Reference or Description
confirmed Section 5.1.3
cancelled Section 5.1.3
tentative Section 5.1.3

9. Acknowledgments

The authors would like to thank the members of CalConnect for their valuable contributions. This specification originated from the work of the API technical committee of CalConnect, the Calendaring and Scheduling Consortium.

10. References

10.1. Normative References

[CLDR] "Unicode Common Locale Data Repository"
[COLORS] "CSS Color Module"
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC2392] Levinson, E., "Content-ID and Message-ID Uniform Resource Locators", RFC 2392, DOI 10.17487/RFC2392, August 1998.
[RFC2397] Masinter, L., "The "data" URL scheme", RFC 2397, DOI 10.17487/RFC2397, August 1998.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002.
[RFC4589] Schulzrinne, H. and H. Tschofenig, "Location Types Registry", RFC 4589, DOI 10.17487/RFC4589, July 2006.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008.
[RFC5545] Desruisseaux, B., "Internet Calendaring and Scheduling Core Object Specification (iCalendar)", RFC 5545, DOI 10.17487/RFC5545, September 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.
[RFC6838] Freed, N., Klensin, J. and T. Hansen, "Media Type Specifications and Registration Procedures", BCP 13, RFC 6838, DOI 10.17487/RFC6838, January 2013.
[RFC6901] Bryan, P., Zyp, K. and M. Nottingham, "JavaScript Object Notation (JSON) Pointer", RFC 6901, DOI 10.17487/RFC6901, April 2013.
[RFC7493] Bray, T., "The I-JSON Message Format", RFC 7493, DOI 10.17487/RFC7493, March 2015.
[RFC8126] Cotton, M., Leiba, B. and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017.
[RFC8259] Bray, T., "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017.
[RFC8288] Nottingham, M., "Web Linking", RFC 8288, DOI 10.17487/RFC8288, October 2017.
[TZDB] "IANA Time Zone Database"

10.2. Informative References

[LINKRELS] "IANA Link Relation Types"
[LOCATIONTYPES] "IANA Location Types Registry"
[MIME] "IANA Media Types"
[RFC3986] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005.
[RFC4122] Leach, P., Mealling, M. and R. Salz, "A Universally Unique IDentifier (UUID) URN Namespace", RFC 4122, DOI 10.17487/RFC4122, July 2005.
[RFC5546] Daboo, C., "iCalendar Transport-Independent Interoperability Protocol (iTIP)", RFC 5546, DOI 10.17487/RFC5546, December 2009.
[RFC6047] Melnikov, A., "iCalendar Message-Based Interoperability Protocol (iMIP)", RFC 6047, DOI 10.17487/RFC6047, December 2010.
[RFC6376] Crocker, D., Hansen, T. and M. Kucherawy, "DomainKeys Identified Mail (DKIM) Signatures", STD 76, RFC 6376, DOI 10.17487/RFC6376, September 2011.
[RFC7265] Kewisch, P., Daboo, C. and M. Douglass, "jCal: The JSON Format for iCalendar", RFC 7265, DOI 10.17487/RFC7265, May 2014.
[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.
[RFC7808] Douglass, M. and C. Daboo, "Time Zone Data Distribution Service", RFC 7808, DOI 10.17487/RFC7808, March 2016.
[RFC7986] Daboo, C., "New Properties for iCalendar", RFC 7986, DOI 10.17487/RFC7986, October 2016.

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