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. It also aims to be unambiguous, extendable, and simple to process. In contrast to the jCal format, which is also based on JSON, JSCalendar is not a direct mapping from iCalendar but defines the data model independently and expands semantics where appropriate. This specification obsoletes IETF RFC 8984.
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 attributes of the calendar entry represented must be described as simple key-value pairs. Simple events are simple to represent; complex events can be modeled accurately.
Wherever possible, there should be only one way to express the desired semantics, reducing complexity.
The data model should avoid ambiguities, which often lead to interoperability issues between implementations.
The data model should be generally compatible with the iCalendar data format IETF RFC 5545 IETF RFC 7986 and extensions, but the specification should add new attributes where the iCalendar format currently lacks expressivity, and drop seldom-used, obsolete, or redundant properties. This means translation with no loss of semantics should be easy with most common iCalendar files.
Extensions, such as new properties and components, should not require updates to this document.
The representation of this data model is defined in the Internet JSON (I-JSON) format IETF RFC 7493, which is a strict subset of the JSON data interchange format IETF RFC 8259. 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.
Motivation and Relation to iCalendar and jCal
The iCalendar data format IETF RFC 5545, a widely deployed interchange format for calendaring and scheduling data, has served calendaring vendors for a long time but contains some ambiguities and pitfalls that cannot be overcome without backward-incompatible changes.
Sources of implementation errors include the following:
iCalendar defines various formats for local times, UTC, and dates.
iCalendar requires custom time zone definitions within a single calendar component.
iCalendar’s definition of recurrence rules is ambiguous and has resulted in differing interpretations, even between experienced calendar developers.
The iCalendar format itself causes interoperability issues due to misuse of CRLF-terminated strings, line continuations, and subtle differences among iCalendar parsers.
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 IETF RFC 7265, 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 time zone’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.
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 IETF RFC 2119 IETF RFC 8174 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 IETF RFC 8259, Section 1.
Some examples in this document contain “partial” JSON documents used for illustrative purposes. In these examples, an ellipsis “…” is used to indicate a portion of the document that has been removed for compactness.
Type Signatures
Type signatures are given for all JSON values in this document. The following conventions are used:
- *
The type is undefined (the value could be any type, although permitted values may be constrained by the context of this value).
- String
This is the JSON string type.
- Number
This is the JSON number type.
- Boolean
This is the JSON boolean type.
- A[B]
The keys are all of type A and the values are all of type B for a JSON object.
- A[]
There is an array of values of type A.
- A|B
The value is either of type A or of type B.
Other types may also be given; their representations are defined elsewhere in this document.
Data Types
In addition to the standard JSON data types, the following data types are used in this specification:
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 IETF RFC 4648, Section 5, excluding the pad character ( =). This means the allowed characters are the ASCII alphanumeric characters ( A-Za-z0-9), hyphen (-), and underscore (_).
In many places in JSCalendar, a JSON map is used where the map keys are of type Id and the map values are all the same type of object. This construction represents an unordered set of objects, with the added advantage that each entry has a name (the corresponding map key). This allows for more concise patching of objects, and, when applicable, for the objects in question to be referenced from other objects within the JSCalendar object. The map keys MUST be preserved across multiple versions of the JSCalendar object.
Unless otherwise specified for a particular property, there are no uniqueness constraints on an Id value (other than, of course, the requirement that you cannot have two values with the same key within a single JSON map). For example, two Event objects might use the same Ids in their respective links properties or, within the same Event object, the same Id could appear in the participants and alerts properties. These situations do not imply any semantic connections among the objects.
Int
Where Int is given as a data type, it means an integer in the range -253+1 ⇐ value ⇐ 2 53-1, the safe range for integers stored in a floating-point double, represented as a JSON Number.
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.
UTCDateTime
This is a string in the date-time IETF RFC 3339 format, with the further restrictions that any letters MUST be in uppercase, 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 conformant, but 2010-10-10T10:10:10.000Z is invalid and is correctly encoded as 2010-10-10T10:10:10Z.
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 with the LocalDateTime comes from the timeZone property of the JSCalendar object. If no time zone is specified, the LocalDateTime is floating. 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 MUST be used.
For example, in the America/Los_Angeles time zone, the date-time 2020-11-01T01:30:00 occurs twice: before the daylight savings time (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), 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 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.
Duration
Where Duration is given as a type, it means a length of time represented by a subset of the ISO 8601 duration format, as specified by the following ABNF IETF RFC 5234:
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-time)
In addition, the duration MUST NOT include fractional second values unless the fraction is non-zero. Fractional second values MUST NOT have trailing zeros to ensure there is only a single representation for each duration.
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:
Add any week or day components of the duration to the date. A week is always the same as seven days.
If a time zone applies to the LocalDateTime, convert it to a UTCDateTime following the semantics in LocalDateTime.
Add any hour, minute, or second components of the duration (in absolute time).
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:
If a time zone applies to the LocalDateTime, convert it to UTC following the semantics in LocalDateTime.
Subtract any hour, minute, or second components of the duration (in absolute time).
Convert the resulting UTCDateTime back to LocalDateTime in the time zone that applies.
Subtract any week or day components of the duration from the date.
If the resulting time does not exist on the date due to a discontinuity in the time zone, use the semantics in LocalDateTime to convert to UTC and back to get a valid LocalDateTime.
These semantics match the iCalendar DURATION value type ( IETF RFC 5545, Section 3.3.6).
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 indicates a time at or after the associated time.
TimeZoneId
Where TimeZoneId is given as a data type, it means a String that is either a time zone name in the IANA Time Zone Database TZDB or a custom time zone identifier defined in the timeZones property of the Group of which the calendar object is a member of.
Where an IANA time zone is specified, the zone rules of the respective zone records apply. Custom time zones are interpreted as described in the timeZones property.
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 the JSON Pointer format IETF RFC 6901. 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:
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).
All parts prior to the last (i.e., the value after the final slash) MUST already exist on the object being patched.
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 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 determines how to apply that patch:
If null, remove the property from the patched object. If the key is not present in the parent, this a no-op.
If non-null, set the value given as the value for this property (this may be a replacement or addition to the object being patched).
A PatchObject does not define its own @type property. An @type property in a patch MUST be handled as any other patched property value.
Implementations MUST reject a PatchObject in its entirety if any of its patches are invalid. Implementations MUST NOT apply partial patches.
The PatchObject format is used to significantly reduce file size and duplicated content when specifying variations to a common object, such as with recurring events or when translating the data into multiple languages. It can also better preserve semantic intent if only the properties that should differ between the two objects are patched. For example, if one person is not going to a particular instance of a regularly scheduled event, in iCalendar, you would have to duplicate the entire event in the override. In JSCalendar, this is a small patch to show the difference. As only this property is patched, if the location of the event is changed, the occurrence will automatically still inherit this.
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. A Relation object has the following properties:
@type
String (mandatory)
This specifies the type of this object. This MUST be Relation.
relation
String[Boolean] (optional, default: empty Object)
This describes how the linked object is related to the linking object. The relation is defined as a set of relation types. If empty, the relationship between the two objects is unspecified.
Keys in the set MUST be one of the following values, specified in the property definition where the Relation object is used, a value registered in the IANA “JSCalendar Enum Values” registry, or a vendor-specific value (see Clause 5.3):
first
The linked object is the first in a series the linking object is part of.
next
The linked object is next in a series the linking object is part of.
child
The linked object is a subpart of the linking object.
parent
The linking object is a subpart of the linked object.
The value for each key in the map MUST be true.
Link
A Link object represents an external resource associated with the linking object. It has the following properties:
@type
String (mandatory)
This specifies the type of this object. This MUST be Link.
href
String (mandatory)
This is a URI IETF RFC 3986 from which the resource may be fetched.
This MAY be a data: URL IETF RFC 2397, but it is recommended that the file be hosted on a server to avoid embedding arbitrarily large data in JSCalendar object instances.
cid
String (optional)
This MUST be a URI in the cid scheme defined in IETF RFC 2392, Section 2. The value MUST be unique across all Link objects in an Event or Task object, but has no meaning beyond that.
contentType
String (optional)
This is the media type IETF RFC 6838 of the resource, if known.
size
UnsignedInt (optional)
This is the size, in octets, of the resource when fully decoded (i.e., the number of octets in the file the user would download), if known. Note that this is an informational estimate, and implementations must be prepared to handle the actual size being quite different when the resource is fetched.
rel
String (optional)
This identifies the relation of the linked resource to the object. If set, the value MUST be a relation type from the IANA “Link Relations” registry LINKRELS, as established in IETF RFC 8288.
display
String (optional)
This describes the intended purpose of a link to an image. If set, the rel property MUST be set to icon. The value MUST be one of the following values, another value registered in the IANA “JSCalendar Enum Values” registry, or a vendor-specific value:
badge
an image meant to be displayed alongside the title of the object
graphic
a full image replacement for the object itself
fullsize
an image that is used to enhance the object
thumbnail
a smaller variant of fullsize to be used when space for the image is constrained
filename
String (optional)
This is the indicative file name when storing the Link contents in a file.
JSCalendar: A JSON Representation of Calendar Data
1. Scope
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.
2. Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
IETF RFC 2119, S. BRADNER. Key words for use in RFCs to Indicate Requirement Levels. 1997. RFC Publisher. https://www.rfc-editor.org/info/rfc2119.
IETF RFC 2392, E. LEVINSON. Content-ID and Message-ID Uniform Resource Locators. 1998. RFC Publisher. https://www.rfc-editor.org/info/rfc2392.
IETF RFC 2397, L. MASINTER. The “data” URL scheme. 1998. RFC Publisher. https://www.rfc-editor.org/info/rfc2397.
IETF RFC 3339, G. KLYNE and C. NEWMAN. Date and Time on the Internet: Timestamps. 2002. RFC Publisher. https://www.rfc-editor.org/info/rfc3339.
IETF RFC 3986, T. BERNERS-LEE, R. FIELDING and L. MASINTER. Uniform Resource Identifier (URI): Generic Syntax. 2005. RFC Publisher. https://www.rfc-editor.org/info/rfc3986.
IETF RFC 4122, P. LEACH, M. MEALLING and R. SALZ. A Universally Unique IDentifier (UUID) URN Namespace. 2005. RFC Publisher. https://www.rfc-editor.org/info/rfc4122.
IETF RFC 4589, H. SCHULZRINNE and H. TSCHOFENIG. Location Types Registry. 2006. RFC Publisher. https://www.rfc-editor.org/info/rfc4589.
IETF RFC 4648, S. JOSEFSSON. The Base16, Base32, and Base64 Data Encodings. 2006. RFC Publisher. https://www.rfc-editor.org/info/rfc4648.
IETF RFC 5234, P. OVERELL. Augmented BNF for Syntax Specifications: ABNF. 2008. RFC Publisher. https://www.rfc-editor.org/info/rfc5234.
IETF RFC 5322, P. RESNICK (ed.). Internet Message Format. 2008. RFC Publisher. https://www.rfc-editor.org/info/rfc5322.
IETF RFC 5545, B. DESRUISSEAUX (ed.). Internet Calendaring and Scheduling Core Object Specification (iCalendar). 2009. RFC Publisher. https://www.rfc-editor.org/info/rfc5545.
IETF RFC 5546, C. DABOO (ed.). iCalendar Transport-Independent Interoperability Protocol (iTIP). 2009. RFC Publisher. https://www.rfc-editor.org/info/rfc5546.
IETF RFC 5646, A. PHILLIPS and M. DAVIS (eds.). Tags for Identifying Languages. 2009. RFC Publisher. https://www.rfc-editor.org/info/rfc5646.
IETF RFC 5870, A. MAYRHOFER and C. SPANRING. A Uniform Resource Identifier for Geographic Locations (’geo’ URI). 2010. RFC Publisher. https://www.rfc-editor.org/info/rfc5870.
IETF RFC 6047, A. MELNIKOV (ed.). iCalendar Message-Based Interoperability Protocol (iMIP). 2010. RFC Publisher. https://www.rfc-editor.org/info/rfc6047.
IETF RFC 6838, N. FREED, J. KLENSIN and T. HANSEN. Media Type Specifications and Registration Procedures. 2013. RFC Publisher. https://www.rfc-editor.org/info/rfc6838.
IETF RFC 6901, K. ZYP. JavaScript Object Notation (JSON) Pointer. 2013. RFC Publisher. https://www.rfc-editor.org/info/rfc6901.
IETF RFC 7493, T. BRAY (ed.). The I-JSON Message Format. 2015. RFC Publisher. https://www.rfc-editor.org/info/rfc7493.
IETF RFC 7529, C. DABOO and G. YAKUSHEV. Non-Gregorian Recurrence Rules in the Internet Calendaring and Scheduling Core Object Specification (iCalendar). 2015. RFC Publisher. https://www.rfc-editor.org/info/rfc7529.
IETF RFC 7808, M. DOUGLASS and C. DABOO. Time Zone Data Distribution Service. 2016. RFC Publisher. https://www.rfc-editor.org/info/rfc7808.
IETF RFC 8126, M. COTTON, B. LEIBA and T. NARTEN. Guidelines for Writing an IANA Considerations Section in RFCs. 2017. RFC Publisher. https://www.rfc-editor.org/info/rfc8126.
IETF RFC 8174, B. LEIBA. Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words. 2017. RFC Publisher. https://www.rfc-editor.org/info/rfc8174.
IETF RFC 8259, T. BRAY (ed.). The JavaScript Object Notation (JSON) Data Interchange Format. 2017. RFC Publisher. https://www.rfc-editor.org/info/rfc8259.
IETF RFC 8288, M. NOTTINGHAM. Web Linking. 2017. RFC Publisher. https://www.rfc-editor.org/info/rfc8288.
IETF RFC 8984, N. JENKINS and R. STEPANEK. JSCalendar: A JSON Representation of Calendar Data. 2021. RFC Publisher. https://www.rfc-editor.org/info/rfc8984.
CLDR, Unicode Common Locale Data Repository, http://cldr.unicode.org/
TZDB, IANA Time Zone Database, https://www.iana.org/time-zones
COLORS, Çelik, T., Lilley, C., and L. Baron, “CSS Color Module Level 3”, W3C Recommendation, June 2018.
3. Terms and definitions
No terms and definitions are listed in this document.
4. JSCalendar Objects
This section describes the calendar object types specified by JSCalendar.
4.1. Event
Media type: application/jscalendar+json;type=event
An Event 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 Clause 6.1.1 property value MUST be Event.
4.2. Task
Media type: application/jscalendar+json;type=task
A Task represents an action item, assignment, to-do item, or work item. It may start and be due at certain points in time, take some estimated time to complete, and recur, none of which is required.
The @type Clause 6.1.1 property value MUST be Task.
4.3. Group
Media type: application/jscalendar+json;type=group
A Group is a collection of Event and/or Task objects. Typically, objects are grouped by topic (e.g., by keywords) or calendar membership.
The @type Clause 6.1.1 property value MUST be Group.
5. Structure of JSCalendar Objects
A JSCalendar object is a JSON object IETF RFC 8259, which MUST be valid I-JSON (a stricter subset of JSON) IETF RFC 7493. 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.
5.1. 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.
5.2. 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:
Custom JSCalendar properties may contain arbitrary JSON values, including arrays. However, equivalence of arrays might or might not depend on the order of elements, depending on the respective property definition.
Several JSCalendar property values are defined as URIs and media types, but normalization of these types is inherently protocol and scheme specific, depending on the use case of the equivalence definition (see IETF RFC 3986, Section 6).
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.
5.3. 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 an @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.
6. 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 Clause 7 describe the set of supported properties per type.
6.1. Metadata Properties
6.1.1. @type
Type: String (mandatory).
This specifies the type this object represents. The allowed value differs by object type and is defined in sections Clause 4.1, Clause 4.2, and Clause 4.3
6.1.2. uid
Type: String (mandatory).
This is a globally unique identifier used to associate objects representing the same object across different systems, calendars, and views. For recurring events and tasks, the UID is associated with the base object and therefore is the same for all occurrences; the combination of the UID with a recurrenceId identifies a particular instance.
The generator of the identifier MUST guarantee that the identifier is unique. IETF RFC 4122 describes a range of established algorithms to generate universally unique identifiers (UUIDs). UUID version 4, described in IETF RFC 4122, Section 4.4, is RECOMMENDED.
For compatibility with UIDs IETF RFC 5545, 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.
6.1.4. prodId
Type: String (optional).
This is 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 MUST ensure that this is a globally unique identifier, using some technique such as an a Formal Public Identifier (FPI) value, as defined in ISO/IEC 9070:1991.
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 nonstandard properties, a practice that is known to cause long-term interoperability problems.
6.1.5. created
Type: UTCDateTime (optional).
This is the date and time this object was initially created.
6.1.6. updated
Type: UTCDateTime (mandatory).
This is the date and time the data in this object was last modified (or its creation date/time if not modified since).
6.1.7. 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 Clause 6.5.9).
This is used as part of iCalendar Transport-independent Interoperability Protocol (iTIP) IETF RFC 5546 to know which version of the object a scheduling message relates to.
6.1.8. method
Type: String (optional).
This is the iTIP IETF RFC 5546 method, in lowercase. This MUST only be present if the JSCalendar object represents an iTIP scheduling message.
6.2. What and Where Properties
6.2.2. description
Type: String (optional, default: empty String).
This is a longer-form text description of the object. The content is formatted according to the descriptionContentType property.
6.2.3. descriptionContentType
Type: String (optional, default: text/plain).
This describes the media type IETF RFC 6838 of the contents of the description property. Media types MUST be subtypes of type text, and SHOULD be text/plain or text/html MEDIATYPES. The media type value MUST NOT include parameters. Descriptions of type text/html MAY contain cid URLs IETF RFC 2392 to reference links in the calendar object by use of the cid property of the Link object.
6.2.4. timeZone
Type: TimeZoneId|null (optional, default: null).
This identifies the time zone the object is scheduled in or is null for floating time. This is either a name from the IANA Time Zone Database TZDB or the TimeZoneId of a custom time zone defined in the Group timeZones property Clause 7.3.3, of which the calendar object is a member of.
If omitted, this MUST be presumed to be null (i.e., floating time).
6.2.5. showWithoutTime
Type: Boolean (optional, default: false).
This 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.
6.2.6. locations
Type: Id[Location] (optional).
This is 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.
@type: String (mandatory)
This specifies the type of this object. This MUST be Location.
uid: String (optional)
This is the globally unique identifier of the location. See Clause 6.1.2 for the definition of this property.
title: String (optional)
This is a short human-readable title of the location.
description: String (optional)
This is a human-readable, plain-text description of this location, such as instructions for accessing it. This may be an address, set of directions, door access code, etc.
locationTypes: String[Boolean] (optional)
This is a set of one or more location types that describe this location. All types MUST be from the “Location Types Registry” LOCATIONTYPES, as defined in IETF RFC 4589. The set is represented as a map, with the keys being the location types. The value for each key in the map MUST be true.
relativeTo: String (optional)
This specifies the relation between this location and the time of the JSCalendar object. This is primarily to allow events representing travel to specify the location of departure (at the start of the event) and location of arrival (at the end); this is particularly important if these locations are in different time zones, as a client may wish to highlight this information for the user.
The start and end values of the relativeTo property each MUST be set in at most one Location (e.g. an event may only start at a single location and may only end at one other).
This MUST be one of the following values, another value registered in the IANA “JSCalendar Enum Values” registry, or a vendor-specific value (see Clause 5.3). Any value the client or server doesn’t understand should be treated the same as if this property is omitted.
start: The event/task described by this JSCalendar object occurs at this location at the time the event/task starts.
end: The event/task described by this JSCalendar object occurs at this location at the time the event/task ends.
timeZone: TimeZoneId (optional)
This is a time zone for this location.
coordinates: String (optional)
This is a geo: URI IETF RFC 5870 for the location.
links: Id[Link] (optional)
This is a map of link ids to Link objects, representing external resources associated with this location, for example a vCard or image. If there are no links, this MUST be omitted (rather than specified as an empty set).
6.3. conferences
Type: Id[Conference] (optional).
This is a map of conference ids to Conference objects, representing online meetings, such as video conferences or chat rooms.
A Conference object has the following properties.
@type: String (mandatory)
This specifies the type of this object. This MUST be Conference.
name: String (optional, default: empty String)
This is the human-readable name of the conference.
description: String (optional)
These are human-readable plain-text instructions for accessing this virtual conference. This may be an access code, etc.
uri: String (mandatory)
This is a URI IETF RFC 3986 that represents how to connect to this conference.
This may be a telephone number (represented using the tel: scheme, e.g., tel:+1-555-555-5555) for a teleconference, a web address for online chat, or any custom URI.
features: String[Boolean] (optional)
A set of features supported by this virtual conference. The set is represented as a map, with the keys being the feature. The value for each key in the map MUST be true.
The feature MUST be one of the following values, another value registered in the IANA “JSCalendar Enum Values” registry, or a vendor-specific value (see Clause 5.3). Any value the client or server doesn’t understand should be treated the same as if this feature is omitted.
audio: Audio conferencing
chat: Chat or instant messaging
feed: Blog or atom feed
moderator: Provides moderator-specific features
phone: Phone conferencing
screen: Screen sharing
video: Video conferencing
6.3.1. links
Type: Id[Link] (optional).
This is a map of link ids to Link objects, representing external resources associated with the object.
Links with a rel of enclosure MUST be considered by the client to be attachments for download.
Links with a rel of describedby MUST be considered by the client to be alternative representations of the description.
Links with a rel of icon MUST be considered by the client to be images that it may use when presenting the calendar data to a user. The display property may be set to indicate the purpose of this image.
6.3.2. locale
Type: String (optional).
This is the language tag, as defined in IETF RFC 5646 that best describes the locale used for the text in the calendar object, if known.
6.3.3. keywords
Type: String[Boolean] (optional).
This is 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.
6.3.4. categories
Type: String[Boolean] (optional).
This is 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 are typically 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.
6.3.5. color
Type: String (optional).
This is 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 COLORS, or an RGB value in hexadecimal notation, as defined in Section 4.2.1 of COLORS.
6.4. 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 base event with rules to generate recurrences, and/or overrides that add extra dates or exceptions to the rules.
The recurrence set is the complete set of instances for an object. It is generated by considering the following properties in order, all of which are optional:
The recurrenceRules property (Clause 6.4.3) generates a set of extra date-times on which the object occurs.
The excludedRecurrenceRules property (Clause 6.4.4) generates a set of date-times that are to be removed from the previously generated set of date-times on which the object occurs.
The recurrenceOverrides property (Clause 6.4.5) defines date-times that are added or excluded to form the final set. (This property may also contain changes to the object to apply to particular instances.)
6.4.1. 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 base event, or added as a key to the recurrenceOverrides property of the base event.
6.4.2. recurrenceIdTimeZone
Type: TimeZoneId|null (optional, default: null).
Identifies the time zone of the main JSCalendar object, of which this JSCalendar object is a recurrence instance. This property MUST be set if the recurrenceId property is set. It MUST NOT be set if the recurrenceId property is not set.
6.4.3. recurrenceRules
Type: RecurrenceRule[] (optional).
This defines a set of recurrence rules (repeating patterns) for recurring calendar objects.
An Event recurs by applying the recurrence rules to the start date-time.
A Task 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 are used, ignoring any duplicates.
A RecurrenceRule object is a JSON object mapping of a RECUR value type in iCalendar IETF RFC 5545 IETF RFC 7529 and has the same semantics. It has the following properties:
@type: String (mandatory)
This specifies the type of this object. This MUST be RecurrenceRule.
frequency: String (mandatory)
This is the time span covered by each iteration of this recurrence rule (see Clause 6.4.3.1 for full semantics). This MUST be one of the following values:
yearly
monthly
weekly
daily
hourly
minutely
secondly
This is the FREQ part from iCalendar, converted to lowercase.
interval: UnsignedInt (optional, default: 1)
This is the interval of iteration periods at which the recurrence repeats. If included, it MUST be an integer >= 1.
This is the INTERVAL part from iCalendar.
rscale: String (optional, default: “gregorian”)
This is the calendar system in which this recurrence rule operates, in lowercase. This MUST be either a CLDR-registered calendar system name CLDR, or a vendor-specific value (see Clause 5.3).
This is the RSCALE part from iCalendar RSCALE IETF RFC 7529, converted to lowercase.
skip: String (optional, default: “omit”)
This is the behavior to use when the expansion of the recurrence produces invalid dates. This property only has an effect if the frequency is “yearly” or “monthly”. It MUST be one of the following values:
omit
backward
forward
This is the SKIP part from iCalendar RSCALE IETF RFC 7529, converted to lowercase.
firstDayOfWeek: String (optional, default: “mo”)
This is the day on which the week is considered to start, represented as a lowercase, abbreviated, and two-letter English day of the week. If included, it MUST be one of the following values:
mo
tu
we
th
fr
sa
su
This is the WKST part from iCalendar.
byDay: NDay[] (optional)
These are days of the week on which to repeat. An NDay object has the following properties:
@type: String (mandatory)
This specifies the type of this object. This MUST be NDay.
day: String (mandatory)
This is a day of the week on which to repeat; the allowed values are the same as for the firstDayOfWeek RecurrenceRule property.
This is the day of the week of the BYDAY part in iCalendar, converted to lowercase.
nthOfPeriod: Int (optional)
If present, rather than representing every occurrence of the weekday defined in the day property, it represents only a specific instance within the recurrence period. The value can be positive or negative, but MUST NOT be zero. A negative integer means the nth-last occurrence within that period (i.e., -1 is the last occurrence, -2 the one before that, etc.).
This is the ordinal part of the BYDAY value in iCalendar (e.g., 1 or -3).
byMonthDay: Int[] (optional)
These are the days of the month on which to repeat. Valid values are between 1 and the maximum number of days any month may have in the calendar given by the “rscale” property, and the negative values of these numbers. For example, in the Gregorian calendar, valid values are 1 to 31 and -31 to -1. Negative values offset from the end of the month. The array MUST have at least one entry if included.
This is the BYMONTHDAY part in iCalendar.
byMonth: String[] (optional)
These are the months in which to repeat. Each entry is a string representation of a number, starting from “1” for the first month in the calendar (e.g., “1” means January with the Gregorian calendar), with an optional “L” suffix (see IETF RFC 7529) for leap months (this MUST be uppercase, e.g., “3L”). The array MUST have at least one entry if included.
This is the BYMONTH part from iCalendar.
byYearDay: Int[] (optional)
These are the days of the year on which to repeat. Valid values are between 1 and the maximum number of days any year may have in the calendar given by the “rscale” property, and the negative values of these numbers. For example, in the Gregorian calendar, valid values are 1 to 366 and -366 to -1. Negative values offset from the end of the year. The array MUST have at least one entry if included.
This is the BYYEARDAY part from iCalendar.
byWeekNo: Int[] (optional)
These are the weeks of the year in which to repeat. Valid values are between 1 and the maximum number of weeks any year may have in the calendar given by the “rscale” property, and the negative values of these numbers. For example, in the Gregorian calendar, valid values are 1 to 53 and -53 to -1. The array MUST have at least one entry if included.
This is the BYWEEKNO part from iCalendar.
byHour: UnsignedInt[] (optional)
These are the hours of the day in which to repeat. Valid values are 0 to 23. The array MUST have at least one entry if included. This is the BYHOUR part from iCalendar.
byMinute: UnsignedInt[] (optional)
These are the minutes of the hour in which to repeat. Valid values are 0 to 59. The array MUST have at least one entry if included.
This is the BYMINUTE part from iCalendar.
bySecond: UnsignedInt[] (optional)
These are the seconds of the minute in which to repeat. Valid values are 0 to 60. The array MUST have at least one entry if included.
+ This is the BYSECOND part from iCalendar.
bySetPosition: Int[] (optional)
These are the occurrences within the recurrence interval to include in the final results. Negative values offset from the end of the list of occurrences. The array MUST have at least one entry if included. This is the BYSETPOS part from iCalendar.
count: UnsignedInt (optional)
These are the number of occurrences at which to range-bound the recurrence. This MUST NOT be included if an until property is specified.
This is the COUNT part from iCalendar.
until: LocalDateTime (optional)
These are the date-time at which to finish recurring. The last occurrence is on or before this date-time. This MUST NOT be included if a count property is specified. Note that if not specified otherwise for a specific JSCalendar object, this date is to be interpreted in the time zone specified in the JSCalendar object’s timeZone property.
This is the UNTIL part from iCalendar.
6.4.3.1. Interpreting Recurrence Rules
A recurrence rule specifies a set of date-times for recurring calendar objects. A recurrence rule has the following semantics. Note that 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.
A set of candidates is generated. This is every second within a period defined by the frequency property value:
yearly: every second from midnight on the first day of a year (inclusive) to midnight the first day of the following year (exclusive).
If skip is not “omit”, the calendar system has leap months and there is a byMonth property, generate candidates for the leap months, even if they don’t occur in this year.
If skip is not “omit” and there is a byMonthDay property, presume each month has the maximum number of days any month may have in this calendar system when generating candidates, even if it’s more than this month actually has.
monthly: every second from midnight on the first day of a month (inclusive) to midnight on the first of the following month (exclusive).
If skip is not “omit” and there is a byMonthDay property, presume the month has the maximum number of days any month may have in this calendar system when generating candidates, even if it’s more than this month actually has.
weekly: every second from midnight (inclusive) on the first day of the week (as defined by the firstDayOfWeek property, or Monday if omitted), to midnight seven days later (exclusive).
daily: every second from midnight at the start of the day (inclusive) to midnight at the end of the day (exclusive).
hourly: every second from the beginning of the hour (inclusive) to the beginning of the next hour (exclusive).
minutely: every second from the beginning of the minute (inclusive) to the beginning of the next minute (exclusive).
secondly: only the second itself.
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, the date-time 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:
byMonth: The date-time is in the given month.
byWeekNo: The date-time is in the nth week of the year. Negative numbers mean the nth last week of the year. This corresponds to weeks according to week numbering, as defined in ISO.8601.2004, with a week defined as a seven-day period, starting on thefirstDayOfWeek property value or Monday if omitted. Week number one of the calendar year is the first week that contains at least four days in that calendar year.
If the date-time is not valid (this may happen when generating candidates with a skip property in effect), it is always eliminated by this property.
byYearDay: The date-time is on the nth day of year. Negative numbers mean the nth last day of the year.
If the date-time is not valid (this may happen when generating candidates with a skip property in effect), it is always eliminated by this property.
byMonthDay: The date-time is on the given day of the month. Negative numbers mean the nth last day of the month.
byDay: The date-time is on the given day of the week. If the day is prefixed by a number, it is the nth occurrence of that day of the week within the month (if frequency is monthly) or year (if frequency is yearly). Negative numbers mean nth last occurrence within that period.
byHour: The date-time has the given hour value.
byMinute: The date-time has the given minute value.
bySecond: The date-time has the given second value.
If a skip property is defined and is not “omit”, there may be candidates that do not correspond to valid dates (e.g., February 31st in the Gregorian calendar). In this case, the properties MUST be considered in the order above and:
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.
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”).
If any valid date produced after applying the skip is already a candidate, eliminate the duplicate. (For example, after adjusting, February 30th and February 31st would both become the same “real” date, so one is eliminated as a duplicate.)
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 indexed from the end of the list, with -1 being the last item, -2 the second from last, etc.
Any date-times before the start date of the event are eliminated (see below for why this might be needed).
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”.)
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:
The initial date-time to which the rule is applied (the start date-time for events or 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.
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 are eliminated from the results in step 4 as outlined above.
The following properties MUST be implicitly added to the rule under the given conditions:
If frequency is not secondly and there is no bySecond property, add a bySecond property with the sole value being the seconds value of the initial date-time.
If frequency is not secondly or minutely, and there is no byMinute property, add a byMinute property with the sole value being the minutes value of the initial date-time.
If frequency is not secondly, minutely or hourly and there is no byHour property, add a byHour property with the sole value being the hours value of the initial date-time.
If frequency is weekly and there is no byDay property, add a byDay property with the sole value being the day of the week of the initial date-time.
If frequency is monthly and there is no byDay property and no byMonthDay property, add a byMonthDay property with the sole value being the day of the month of the initial date-time.
If frequency is yearly and there is no byYearDay property:
If there are no byMonth or byWeekNo properties, and either there is a byMonthDay property or there is no byDay property, add a byMonth property with the sole value being the month of the initial date-time.
If there is no byMonthDay, byWeekNo, or byDay properties, add a byMonthDay property with the sole value being the day of the month of the initial date-time.
If there is a byWeekNo property and no byMonthDay or byDay properties, add a byDay property with the sole value being the day of the week of the initial date-time.
6.4.4. excludedRecurrenceRules
Type: RecurrenceRule[] (optional).
This 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 Clause 6.4.3), with the exception that the initial date-time to which the rule is applied (the “start” date-time for events or 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 is then removed from those generated by the recurrenceRules property, as described in Clause 6.4.
6.4.5. recurrenceOverrides
Type: LocalDateTime[PatchObject] (optional).
Maps recurrence ids (the date-time produced by the recurrence rule) to the overridden properties of the recurrence instance.
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 of an occurrence to be true, this occurrence is omitted from the final set of recurrences for the calendar object (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:
@type
excludedRecurrenceRules
method
privacy
prodId
recurrenceId
recurrenceIdTimeZone
recurrenceOverrides
recurrenceRules
relatedTo
replyTo
sentFrom
timeZones
uid
6.4.6. excluded
Type: Boolean (optional, default: false).
This defines if this object is an overridden, excluded instance of a recurring JSCalendar object (see Clause 6.4.5). If this property value is true, this calendar object instance MUST be removed from the occurrence expansion. The absence of this property, or the presence of its default value false, indicates that this instance MUST be included in the occurrence expansion. If this property is set, then the recurrenceId property MUST be set.
6.6. Alerts Properties
6.6.1. 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.
6.6.2. alerts
Type: Id[Alert] (optional).
This is 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:
@type: String (mandatory)
This specifies the type of this object. This MUST be Alert.
uid: String (optional)
This is the globally unique identifier of the alert. See Clause 6.1.2 for the definition of this property.
trigger: OffsetTrigger|AbsoluteTrigger|UnknownTrigger (mandatory)
This defines when to trigger the alert. New types may be defined in future documents.
An OffsetTrigger object has the following properties:
@type: String (mandatory)
This specifies the type of this object. This MUST be OffsetTrigger.
offset: SignedDuration (mandatory).
This defines the offset at which to trigger the alert relative to the time property defined in the relativeTo property of the alert. Negative durations signify alerts before the time property; positive durations signify alerts after the time property.
relativeTo: String (optional, default: start)
This specifies the time property that the alert offset is relative to. The value MUST be one of:
start: triggers the alert relative to the start of the calendar object
end: triggers the alert relative to the end/due time of the calendar object
An AbsoluteTrigger object has the following properties:
@type: String (mandatory)
This specifies the type of this object. This MUST be AbsoluteTrigger.
when: UTCDateTime (mandatory).
This defines a specific UTC date-time when the alert is triggered.
An UnknownTrigger object is an object that contains a @type property whose value is not recognized (i.e., not OffsetTrigger or AbsoluteTrigger) plus zero or more other properties. This is for compatibility with client extensions and future specifications. Implementations SHOULD NOT trigger for trigger types they do not understand, but MUST preserve them.
acknowledged: UTCDateTime (optional)
This records when an alert was last acknowledged. This is set when the user has dismissed the alert; other clients that sync this property SHOULD automatically dismiss or suppress duplicate alerts (alerts with the same alert id that triggered on or before this date-time).
For a recurring calendar object, setting the acknowledged property MUST NOT add a new override to the recurrenceOverrides property. If the alert is not already overridden, the acknowledged property MUST be set on the alert in the base event/task.
Certain kinds of alert action may not provide feedback as to when the user sees them, for example, email-based alerts. For those kinds of alerts, this property MUST be set immediately when the alert is triggered and the action successfully carried out.
relatedTo: String[Relation] (optional)
This relates this alert to other alerts in the same JSCalendar object. If the user wishes to snooze an alert, the application MUST create an alert to trigger after snoozing. This new snooze alert MUST set a parent relation to the identifier of the original alert.
action: String (optional, default: display)
This describes how to alert the user.
The value MUST be at most one of the following values, a value registered in the IANA “JSCalendar Enum Values” registry, or a vendor-specific value (see Clause 5.3):
display: The alert should be displayed as appropriate for the current device and user context. ** email: The alert should trigger an email sent out to the user, notifying them of the alert. This action is typically only appropriate for server implementations.
6.7. Multilingual Properties
6.7.1. localizations
Type: String[PatchObject] (optional).
A map where each key is a language tag IETF RFC 5646, and the value is a PatchObject PatchObject, that localizes the patch target properties in that language. The value type of the patched property MUST be String and the property SHOULD contain human-readable text. A patch pointer MUST NOT have the prefix recurrenceOverrides; instead, the override should define its own localizations property.
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 workflow and requirements.
7. Type-specific JSCalendar Properties
7.1. Event Properties
In addition to the common JSCalendar object properties Clause 6, an Event has the following properties:
7.1.1. start
Type: LocalDateTime (mandatory)
This is the date/time the event starts in the event’s time zone (as specified in the timeZone property, see Clause 6.2.4.
7.1.2. duration
Type: Duration (optional, default: PT0S)
This is the zero or positive duration of the event in the event’s start time zone. The end time of an event can be found by adding the duration to the event’s start time.
A Event MAY involve start and end locations that are in different time zones (e.g., a transcontinental flight). This can be expressed using the relativeTo and timeZone properties of the Event’s Location objects (see Clause 6.2.6).
7.1.3. status
Type: String (optional, default: confirmed).
This is the scheduling status (Clause 6.5) of a Event. If set, it MUST be one of the following values, another value registered in the IANA “JSCalendar Enum Values” registry, or a vendor-specific value (see Clause 5.3):
confirmed: indicates the event is definitely happening.
cancelled: indicates the event has been cancelled.
tentative: indicates the event may happen.
7.2. Task Properties
In addition to the common JSCalendar object properties Clause 6, a Task has the following properties:
7.2.1. due
Type: LocalDateTime (optional).
This is the date/time the task is due in the task’s time zone.
7.2.2. start
Type: LocalDateTime (optional).
This is the date/time the task should start in the task’s time zone.
7.2.3. estimatedDuration
Type: Duration (optional).
This specifies the estimated positive duration of time the task takes to complete.
7.2.4. percentComplete
Type: UnsignedInt (optional).
This represents the percent completion of the task overall. The property value MUST be a positive integer between 0 and 100.
7.2.5. progress
Type: String (optional).
This defines the progress of this task. If omitted, the default progress ( Clause 6.5) of a Task is defined as follows (in order of evaluation):
completed: if the progress property value of all participants is completed.
failed: if at least one progress property value of a participant is failed.
in-process: if at least one progress property value of a participant is in-process.
needs-action: if none of the other criteria match.
If set, it MUST be one of the following values, another value registered in the IANA “JSCalendar Enum Values” registry, or a vendor-specific value (see Clause 5.3):
needs-action: indicates the task needs action.
in-process: indicates the task is in process.
completed: indicates the task is completed.
failed: indicates the task failed.
cancelled: indicates the task was cancelled.
7.2.6. progressUpdated
Type: UTCDateTime (optional).
This specifies the date/time the progress property of either the task overall ( Clause 7.2.5) or a specific participant (Clause 6.5.9) 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 Task into a current, single instance of Task with this instance progress update time and a future recurring instance. See also Clause 6.1.3 on splitting.
7.3. Group Properties
Group supports the following common JSCalendar Clause 6 properties:
@type
uid
prodId
created
updated
title
description
descriptionContentType
links
locale
keywords
categories
color
timeZones
In addition, the following Group-specific properties are supported:
7.3.1. entries
Type: (Task|Event)[] (mandatory).
This is a collection of group members. Implementations MUST ignore entries of unknown type.
7.3.2. source
Type: String (optional).
This is the source from which updated versions of this group may be retrieved. The value MUST be a URI.
7.3.3. timeZones
Type: TimeZoneId[TimeZone] (optional).
This property defines custom time zones, in contrast to standard timezone definitions in the IANA Time Zone Database TZDB. Members of the group may refer to these time zones using the keys in this property. Each key in the map MUST start with the / (47) character, followed by the value of the TimeZone tzId property.
A TimeZone object maps a VTIMEZONE component from iCalendar, and the semantics are as defined in IETF RFC 5545. A valid time zone MUST define at least one transition rule in the standard or daylight property. Its properties are:
@type: String (mandatory)
This specifies the type of this object. This MUST be TimeZone.
tzId: String (mandatory)
This is the TZID property from iCalendar. Note that this implies that the value MUST be a valid paramtext value as specified in IETF RFC 5545, Section 3.1.
updated: UTCDateTime (optional)
This is the LAST-MODIFIED property from iCalendar.
url: String (optional)
This is the TZURL property from iCalendar.
validUntil: UTCDateTime (optional)
This is the TZUNTIL property from iCalendar, specified in IETF RFC 7808.
aliases: String[Boolean] (optional)
This maps the TZID-ALIAS-OF properties from iCalendar, specified in IETF RFC 7808, to a JSON set of aliases. The set is represented as an object, with the keys being the aliases. The value for each key in the map MUST be true.
standard: TimeZoneRule[] (optional)
This the STANDARD sub-components from iCalendar. The order MUST be preserved during conversion.
daylight: TimeZoneRule[] (optional)
This the DAYLIGHT sub-components from iCalendar. The order MUST be preserved during conversion.
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:
@type: String (mandatory)
This specifies the type of this object. This MUST be TimeZoneRule.
start: LocalDateTime (mandatory)
This is the DTSTART property from iCalendar.
offsetFrom: String (mandatory)
This is the TZOFFSETFROM property from iCalendar.
offsetTo: String (mandatory)
This is the TZOFFSETTO property from iCalendar.
recurrenceRules: RecurrenceRule[] (optional)
This is the RRULE property mapped, as specified in Clause 6.4.3. During recurrence rule evaluation, the until property value MUST be interpreted as a local time in the UTC time zone.
recurrenceOverrides: LocalDateTime[PatchObject] (optional)
This maps the RDATE properties from iCalendar. The set is represented as an object, with the keys being the recurrence dates. The patch object MUST be the empty JSON object ({}).
names: String[Boolean] (optional)
This maps the TZNAME properties from iCalendar to a JSON set. The set is represented as an object, with the keys being the names, excluding any tznparam component from iCalendar. The value for each key in the map MUST be true.
comments: String[] (optional).
This maps the COMMENT properties from iCalendar. The order MUST be preserved during conversion.
8. 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.
8.1. Simple Event
This example illustrates a simple one-time event. It specifies a one-time event that begins on January 15, 2020 at 1 pm New York local time and ends after 1 hour.
{
"@type": "Event",
"uid": "a8df6573-0474-496d-8496-033ad45d7fea",
"updated": "2020-01-02T18:23:04Z",
"title": "Some event",
"start": "2020-01-15T13:00:00",
"timeZone": "America/New_York",
"duration": "PT1H"
}
8.2. Simple Task
This example illustrates a simple task for a plain to-do item.
{
"@type": "Task",
"uid": "2a358cee-6489-4f14-a57f-c104db4dc2f2",
"updated": "2020-01-09T14:32:01Z",
"title": "Do something"
}
8.3. Simple Group
This example illustrates a simple calendar object group that contains an event and a task.
{
"@type": "Group",
"uid": "bf0ac22b-4989-4caf-9ebd-54301b4ee51a",
"updated": "2020-01-15T18:00:00Z",
"name": "A simple group",
"entries": [{
"@type": "Event",
"uid": "a8df6573-0474-496d-8496-033ad45d7fea",
"updated": "2020-01-02T18:23:04Z",
"title": "Some event",
"start": "2020-01-15T13:00:00",
"timeZone": "America/New_York",
"duration": "PT1H"
},
{
"@type": "Task",
"uid": "2a358cee-6489-4f14-a57f-c104db4dc2f2",
"updated": "2020-01-09T14:32:01Z",
"title": "Do something"
}]
}
8.4. 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"
}]
}
8.5. Task with a Due Date
This example illustrates a task with a due date. It is a reminder to buy groceries before 6 pm Vienna local time on January 19, 2020. The calendar user expects to need 1 hour for shopping.
{
"...": "",
"title": "Buy groceries",
"due": "2020-01-19T18:00:00",
"timeZone": "Europe/Vienna",
"estimatedDuration": "PT1H"
}
8.6. 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, 2020 at 9 am 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": "2020-04-01T09:00:00",
"timeZone": "Europe/Berlin",
"duration": "PT10H30M",
"locations": {
"1": {
"@type": "Location",
"rel": "start",
"name": "Frankfurt Airport (FRA)"
},
"2": {
"@type": "Location",
"rel": "end",
"name": "Narita International Airport (NRT)",
"timeZone": "Asia/Tokyo"
}
}
}
8.7. Floating-Time Event (with Recurrence)
This example illustrates the use of floating time. Since January 1, 2020, a calendar user blocks 30 minutes every day to practice yoga at 7 am local time in whatever time zone the user is located on that date.
{
"...": "",
"title": "Yoga",
"start": "2020-01-01T07:00:00",
"duration": "PT30M",
"recurrenceRules": [{
"@type": "RecurrenceRule",
"frequency": "daily"
}]
}
8.8. Event with Multiple Locations and Localization
This example illustrates an event that happens at both a physical location and online. 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": "2020-07-04T17:00:00",
"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"
}
},
"conferences": {
"conf1": {
"@type": "Conference",
"name": "Free live Stream from Music Bowl",
"uri": "https://stream.example.com/the_band_2020"
}
},
"localizations": {
"de": {
"title": "Live von der Music Bowl: The Band!",
"description": "Schau dir das größte Musikereignis an!",
"conferences/vloc1/name":
"Gratis Live-Stream aus der Music Bowl"
}
}
}
8.9. 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, 2020 at 9 am London time and occurs every week until June 24, 2020. 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 10 am. Also, the location of the exam differs from the usual location. On April 1, no course is held. On January 7 at 2 pm, there is an optional introduction course, which occurs before the first regular lecture.
{
"...": "",
"title": "Calculus I",
"start": "2020-01-08T09:00:00",
"timeZone": "Europe/London",
"duration": "PT1H30M",
"locations": {
"mlab": {
"@type": "Location",
"title": "Math lab room 1",
"description": "Math Lab I, Department of Mathematics"
}
},
"recurrenceRules": [{
"@type": "RecurrenceRule",
"frequency": "weekly",
"until": "2020-06-24T09:00:00"
}],
"recurrenceOverrides": {
"2020-01-07T14:00:00": {
"title": "Introduction to Calculus I (optional)"
},
"2020-04-01T09:00:00": {
"excluded": true
},
"2020-06-25T09:00:00": {
"title": "Calculus I Exam",
"start": "2020-06-25T10:00:00",
"duration": "PT2H",
"locations": {
"auditorium": {
"@type": "Location",
"title": "Big Auditorium",
"description": "Big Auditorium, Other Road"
}
}
}
}
}
8.10. Recurring Event with Participants
This example illustrates scheduled events. A team meeting occurs every week since January 8, 2020 at 9 am Johannesburg time. The event owner also chairs the event. Participants meet in an online meeting. An attendee has accepted the invitation, but is unavailable on March 4, 2020 and declined participation for this occurrence.
{
"...": "",
"title": "FooBar team meeting",
"start": "2020-01-08T09:00:00",
"timeZone": "Africa/Johannesburg",
"duration": "PT1H",
"conferences": {
"0": {
"@type": "Conference",
"name": "ChatMe meeting room",
"uri": "https://chatme.example.com?id=1234567&pw=a8a24627b63d"
}
},
"recurrenceRules": [{
"@type": "RecurrenceRule",
"frequency": "weekly"
}],
"replyTo": {
"imip": "mailto:f245f875-7f63-4a5e-a2c8@schedule.example.com"
},
"participants": {
"dG9tQGZvb2Jhci5xlLmNvbQ": {
"@type": "Participant",
"name": "Tom Tool",
"email": "tom@foobar.example.com",
"sendTo": {
"imip": "mailto:tom@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": {
"2020-03-04T09:00:00": {
"participants/dG9tQGZvb2Jhci5xlLmNvbQ/participationStatus":
"declined"
}
}
}
9. Security Considerations
Calendaring and scheduling information is very privacy sensitive. It can reveal the social network of a user, location information of this user and those in their social network, identity and credentials information, and patterns of behavior of the user in both the physical and cyber realm. Additionally, calendar events and tasks can influence the physical location of a user or their cyber behavior within a known time window. Its transmission and storage must be done carefully to protect it from possible threats, such as eavesdropping, replay, message insertion, deletion, modification, and on-path 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 organizer 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 and ensure the change comes from an authorized entity.
This document only defines the data format; such considerations are primarily the concern of the API or method of storage and transmission of such files.
9.1. 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.
Events recur in the event’s time zone. If the user is in a different time zone, daylight saving transitions may cause an event that normally occurs at, for example, 9 am to suddenly shift an hour earlier. This may be used in an attempt to cause a participant to miss an important meeting. User agents must be careful to translate date-times correctly between time zones and may wish to call out unexpected changes in the time of a recurring event.
9.2. JSON Parsing
The security considerations of IETF RFC 8259 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.
9.3. URI Values
Several JSCalendar properties contain URIs as values, and processing these properties requires extra care. IETF RFC 3986, Section 7 discusses security risks related to URIs.
Fetching remote resources carries inherent risks. Connections must only be allowed on well-known ports, using allowed protocols (generally, just HTTP/HTTPS on their default ports). The URL must be resolved externally and not allowed to access internal resources. Connecting to an external source reveals IP (and therefore often location) information.
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.
9.4. 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 DomainKeys Identified Mail (DKIM) IETF RFC 6376, can help establish the source of messages and associate the data with existing relationships (such as an address book contact). However, misclassifications are always possible and providing a mechanism for users to quickly correct this is advised.
Confusable unicode characters may be used to trick a user into trusting a JSCalendar file that appears to come from a known contact but is actually from a similar-looking source controlled by an attacker.
9.5. Duplication
It is important for calendar systems to maintain the UID of an event when updating it to avoid an unexpected duplication of events. 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.
9.6. 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.
10. IANA Considerations
10.1. 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. The allowed parameter values correspond to the @type property of the JSON-formatted JSCalendar object in the body:
- event
The @type property value MUST be Event.
- task
The @type property value MUST be Task.
- group
The @type property value MUST be Group.
No other parameter values are allowed. The parameter MUST NOT occur more than once.
Optional parameters
none
Encoding considerations
This is the same as the encoding considerations of application/json, as specified in IETF RFC 8259, Section 11.
Security considerations
See Clause 9 of this document.
Interoperability considerations
While JSCalendar is designed to avoid ambiguities as much as possible, when converting objects from other calendar formats to/from JSCalendar, it is possible that differing representations for the same logical data or ambiguities in interpretation might arise. The semantic equivalence of two JSCalendar objects may be determined differently by different applications, for example, where URL values differ in case between the two objects.
Published specification
RFC 8984
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
A JSON Pointer fragment identifier may be used, as defined in IETF RFC 6901, Section 6.
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
Intended usage
COMMON
Restrictions on usage
N/A
Author
See the “Author’s Address” section of this document.
Change controller
IETF
10.2. Changes to the “JSCalendar Properties” Registry
When IETF RFC 8984 was published, IANA has created the “JSCalendar Properties” registry to allow interoperability of extensions to JSCalendar objects. As this RFC document obsoletes IETF RFC 8984 the IANA registry contents and update rules shall be completely replaced with the following definitions.
This registry follows the Expert Review process (IETF RFC 8126, Section 4.5). If the “Intended Usage” 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 usage of common, reserved, or obsolete. IANA will list registrations with a common usage designation prominently and separately from those with other intended usage 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 check it is coherent 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 specification, leading to increased interoperability.
10.2.1. 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.
Property 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.
10.2.2. Submit Request to IANA
Registration requests can be sent to <iana@iana.org>.
10.2.3. 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 IETF RFC 8126, Section 4.6, 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.
10.2.4. Change Procedures
Once a JSCalendar property has been published by 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 usage” field; such properties will be clearly marked in the IANA registry.
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 IANA; this can be done without discussion or review.
10.2.5. “JSCalendar Properties” Registry Template
Property Name
This is the name of the property. The property name MUST NOT already be registered for any of the object types listed in the “Property Context” field of this registration. Other object types MAY already have registered a different property with the same name; however, the same name SHOULD only be used when the semantics are analogous.
Property Type
This is the type of this property, using type signatures, as specified in Type Signatures. The property type MUST be registered in the “JSCalendar Types” registry.
Property Context
This is a comma-separated list of JSCalendar object types this property is allowed on.
Reference or Description
This is a brief description or RFC number and section reference where the property is specified (omitted for “reserved” property names).
Intended Usage
This may be “common”, “reserved”, or “obsolete”.
Change Controller
This is who may request a change to this entry’s definition ( IETF for RFCs from the IETF stream).
10.3. 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”.
Table 1 — Initial Contents of the “JSCalendar Properties” Registry
| Property Name | Property Type | Property Context | Reference or Description |
|---|---|---|---|
| @type | String | Event, Task, Group, AbsoluteTrigger, Alert, Link, Location, NDay, OffsetTrigger, Participant, RecurrenceRule, Relation, TimeZone, TimeZoneRule, Conference | Clause 6.1.1, Clause 6.6.2, Link, Clause 6.2.6, Clause 6.5.9, Clause 6.4.3, Relation, Clause 7.3.3, Clause 6.3 |
| acknowledged | UTCDateTime | Alert | Clause 6.6.2 |
| action | String | Alert | Clause 6.6.2 |
| alerts | Id[Alert] | Event, Task | Clause 6.6.2 |
| aliases | String[Boolean] | TimeZone | Clause 7.3.3 |
| byDay | NDay[] | RecurrenceRule | Clause 6.4.3 |
| byHour | UnsignedInt[] | RecurrenceRule | Clause 6.4.3 |
| byMinute | UnsignedInt[] | RecurrenceRule | Clause 6.4.3 |
| byMonth | String[] | RecurrenceRule | Clause 6.4.3 |
| byMonthDay | Int[] | RecurrenceRule | Clause 6.4.3 |
| bySecond | UnsignedInt[] | RecurrenceRule | Clause 6.4.3 |
| bySetPosition | Int[] | RecurrenceRule | Clause 6.4.3 |
| byWeekNo | Int[] | RecurrenceRule | Clause 6.4.3 |
| byYearDay | Int[] | RecurrenceRule | Clause 6.4.3 |
| categories | String[Boolean] | Event, Task, Group | Clause 6.3.4 |
| cid | String | Link | Link |
| color | String | Event, Task, Group | Clause 6.3.5 |
| comments | String[] | TimeZoneRule | Clause 7.3.3 |
| conferences | Id [Conference] | Event, Task, Participant | Clause 6.3 |
| contentType | String | Link | Link |
| coordinates | String | Location | Clause 6.2.6 |
| count | UnsignedInt | RecurrenceRule | Clause 6.4.3 |
| created | UTCDateTime | Event, Task, Group | Clause 6.1.5 |
| day | String | NDay | Clause 6.4.3 |
| daylight | TimeZoneRule[] | TimeZone | Clause 7.3.3 |
| delegatedFrom | Id[Boolean] | Participant | Clause 6.5.9 |
| delegatedTo | Id[Boolean] | Participant | Clause 6.5.9 |
| description | String | Event, Task, Location, Participant, Conference | Clause 6.2.2, Clause 6.2.6, Clause 6.5.9, Clause 6.3 |
| description ContentType | String | Event, Task | Clause 6.2.3 |
| display | String | Link | Link |
| due | LocalDateTime | Task | Clause 7.2.1 |
| duration | Duration | Event | Clause 7.1.2 |
| String | Participant | Clause 6.5.9 | |
| entries | (Task|Event)[] | Group | Clause 7.3.1 |
| estimatedDuration | Duration | Task | Clause 7.2.3 |
| excluded | Boolean | Event, Task | Clause 6.4.6 |
| excluded RecurrenceRules | RecurrenceRule[] | Event, Task | Clause 6.4.4 |
| expectReply | Boolean | Participant | Clause 6.5.9 |
| features | String[Boolean] | Conference | Clause 6.3 |
| firstDayOfWeek | String | RecurrenceRule | Clause 6.4.3 |
| freeBusyStatus | String | Event, Task | Clause 6.5.2 |
| frequency | String | RecurrenceRule | Clause 6.4.3 |
| href | String | Link | Link |
| interval | UnsignedInt | RecurrenceRule | Clause 6.4.3 |
| invitedBy | Id | Participant | Clause 6.5.9 |
| keywords | String[Boolean] | Event, Task, Group | Clause 6.3.3 |
| kind | String | Participant | Clause 6.5.9 |
| language | String | Participant | Clause 6.5.9 |
| links | Id[Link] | Group, Event, Task, Location, Participant | Clause 6.3.1, Clause 6.2.6, Clause 6.5.9 |
| locale | String | Group, Event, Task | Clause 6.3.2 |
| localizations | String [PatchObject] | Event, Task | Clause 6.7.1 |
| locations | Id[Location] | Event, Task, Participant | Clause 6.2.6, Clause 6.5.9 |
| locationTypes | String[Boolean] | Location | Clause 6.2.6 |
| memberOf | Id[Boolean] | Participant | Clause 6.5.9 |
| method | String | Event, Task | Clause 6.1.8 |
| name | String | Location, Conference, Participant | Clause 6.2.6, Clause 6.3, Clause 6.5.9 |
| names | String[Boolean] | TimeZoneRule | Clause 7.3.3 |
| nthOfPeriod | Int | NDay | Clause 6.4.3 |
| offset | SignedDuration | OffsetTrigger | Clause 6.6.2 |
| offsetFrom | UTCDateTime | TimeZoneRule | Clause 7.3.3 |
| offsetTo | UTCDateTime | TimeZoneRule | Clause 7.3.3 |
| participants | Id[Participant] | Event, Task | Clause 6.5.9 |
| participation Comment | String | Participant | Clause 6.5.9 |
| participationStatus | String | Participant | Clause 6.5.9 |
| percentComplete | UnsignedInt | Task, Participant | Clause 7.2.4 |
| priority | Int | Event, Task | Clause 6.5.1 |
| privacy | String | Event, Task | Clause 6.5.3 |
| prodId | String | Event, Task, Group | Clause 6.1.4 |
| progress | String | Task, Participant | Clause 7.2.5 |
| progressUpdated | UTCDateTime | Task, Participant | Clause 7.2.6 |
| recurrenceId | LocalDateTime | Event, Task | Clause 6.4.1 |
| recurrenceIdTimeZone | TimeZoneId|null | Event, Task | Clause 6.4.2 |
| recurrenceOverrides | LocalDateTime [PatchObject] | Event, Task, TimeZoneRule | Clause 6.4.5, Clause 7.3.3 |
| recurrenceRules | RecurrenceRule[] | Event, Task, TimeZoneRule | Clause 6.4.3, Clause 7.3.3 |
| rel | String | Link | Link |
| relatedTo | String[Relation] | Event, Task, Alert | Clause 6.1.3, Clause 6.6.2 |
| relation | String[Boolean] | Relation | Relation |
| relativeTo | String | OffsetTrigger, Location | Clause 6.6.2, Clause 6.2.6 |
| replyTo | String[String] | Event, Task | Clause 6.5.4 |
| replyToScheduleAgent | String | Event, Task | Clause 6.5.5 |
| replyToScheduleForceSend | Boolean | Event, Task | Clause 6.5.6 |
| replyToScheduleStatus | String[] | Event, Task | Clause 6.5.7 |
| requestStatus | String | Event, Task | Clause 6.5.10 |
| roles | String[Boolean] | Participant | Clause 6.5.9 |
| rscale | String | RecurrenceRule | Clause 6.4.3 |
| sentFrom | String | Event, Task, Participant | Clause 6.5.8, Clause 6.5.9 |
| standard | TimeZoneRule[] | TimeZone | Clause 7.3.3 |
| start | LocalDateTime | TimeZoneRule | Clause 7.3.3 |
| scheduleAgent | String | Participant | Clause 6.5.9 |
| scheduleForceSend | Boolean | Participant | Clause 6.5.9 |
| scheduleSequence | UnsignedInt | Participant | Clause 6.5.9 |
| scheduleStatus | String[] | Participant | Clause 6.5.9 |
| scheduleUpdated | UTCDateTime | Participant | Clause 6.5.9 |
| sendTo | String[String] | Participant | Clause 6.5.9 |
| sequence | UnsignedInt | Event, Task | Clause 6.1.7 |
| showWithoutTime | Boolean | Event, Task | Clause 6.2.5 |
| size | UnsignedInt | Link | Link |
| skip | String | RecurrenceRule | Clause 6.4.3 |
| source | String | Group | Clause 7.3.2 |
| start | LocalDateTime | Event, Task | Clause 7.1.1, Clause 7.2.2 |
| status | String | Event | Clause 7.1.3 |
| timeZone | TimeZoneId|null | Event, Task, Location | Clause 6.2.4, Clause 6.2.6 |
| timeZones | TimeZoneId [TimeZone] | Group | Clause 7.3.3 |
| title | String | Event, Task, Group, Link | Clause 6.2.1 |
| trigger | OffsetTrigger| AbsoluteTrigger| UnknownTrigger | Alert | Clause 6.6.2 |
| tzId | String | TimeZone | Clause 7.3.3 |
| uid | String | Event, Task, Group, Alert, Location | Clause 6.1.2 |
| until | LocalDateTime | RecurrenceRule | Clause 6.4.3 |
| updated | UTCDateTime | Event, Task, Group | Clause 6.1.6 |
| uri | String | Conference | Clause 6.3 |
| url | String | TimeZone | Clause 7.3.3 |
| useDefaultAlerts | Boolean | Event, Task | Clause 6.6.1 |
| validUntil | UTCDateTime | TimeZone | Clause 7.3.3 |
| when | UTCDateTime | AbsoluteTrigger | Clause 6.6.2 |
10.3.1. Changes to the “JSCalendar Types” Registry
When IETF RFC 8984 was published, IANA has created the “JSCalendar Types” registry to avoid name collisions and provide a complete reference for all data types used for JSCalendar property values. As this RFC document obsoletes IETF RFC 8984 the IANA registry contents shall be completely replaced with the following definitions.
The registration process is the same as for the “JSCalendar Properties” registry, as defined in Clause 10.2.
10.3.2. “JSCalendar Types” Registry Template
Type Name
the name of the type
Reference or Description
a brief description or RFC number and section reference where the Type is specified (may be omitted for “reserved” type names)
Intended Use
common, reserved, or obsolete
Change Controller
who may request a change to this entry’s definition (IETF for RFCs from the IETF stream)
10.4. 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”.
Table 2 — Initial Contents for the “JSCalendar Types” Registry
| Type Name | Reference or Description |
|---|---|
| Alert | Clause 6.6.2 |
| Boolean | Type Signatures |
| Duration | Duration |
| Id | Id |
| Int | Int |
| LocalDateTime | LocalDateTime |
| Link | Link |
| Location | Clause 6.2.6 |
| NDay | Clause 6.4.3 |
| Number | Type Signatures |
| Participant | Clause 6.5.9 |
| PatchObject | PatchObject |
| RecurrenceRule | Clause 6.4.3 |
| Relation | Relation |
| SignedDuration | SignedDuration |
| String | Type Signatures |
| TimeZone | Clause 7.3.3 |
| TimeZoneId | TimeZoneId |
| TimeZoneRule | Clause 7.3.3 |
| UnsignedInt | UnsignedInt |
| UTCDateTime | UTCDateTime |
| Conference | Clause 6.3 |
10.5. Changes to the “JSCalendar Enum Values” Registry
When IETF RFC 8984 was published, IANA has created the “JSCalendar Enum Values” registry to allow interoperable extension of semantics for properties with enumerable values. As this RFC document obsoletes IETF RFC 8984 the IANA registry contents shall be completely replaced with the following definitions.
Each property with enum values has 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 Clause 10.2.
10.5.1. “JSCalendar Enum Values” Registry Property Template
This template is for adding a subregistry for a new enumerable property to the “JSCalendar Enum” registry.
Property Name
These are the name(s) of the property or properties where these values may be used. This MUST be registered in the “JSCalendar Properties” registry.
Context
This is the list of allowed object types where the property or properties may appear, as registered in the “JSCalendar Properties” registry. This disambiguates where there may be two distinct properties with the same name in different contexts.
Change Controller
(IETF for properties defined in RFCs from the IETF stream).
Initial Contents
This is the initial list of defined values for this enum, using the template defined in Clause 10.5.2. A subregistry will be created with these values for this property name/context tuple.
10.5.2. “JSCalendar Enum Values” Registry Value Template
This template is for adding a new enum value to a subregistry in the JSCalendar Enum registry.
Enum Value
the verbatim value of the enum
Reference or Description
a brief description or RFC number and section reference for the semantics of this value
10.5.3. Initial Contents for the “JSCalendar Enum Values” registry
For each subregistry created in this section, all RFC section references are for this document.
Property Name
action
Context
Alert
Change Controller
IETF
Initial Contents
Table 3 — JSCalendar Enum Values for action (Context: Alert)
Enum Value Reference or Description display Clause 6.6.2 email Clause 6.6.2 Property Name
display
Context
Link
Change Controller
IETF
Initial Contents
Table 4 — JSCalendar Enum Values for display (Context: Link)
Enum Value Reference or Description badge Link graphic Link fullsize Link thumbnail Link Property Name
features
Context
VirtualLocation
Change Controller
IETF
Initial Contents
Table 5 — JSCalendar Enum Values for features (Context: Conference)
Enum Value Reference or Description audio Clause 6.3 chat Clause 6.3 feed Clause 6.3 moderator Clause 6.3 phone Clause 6.3 screen Clause 6.3 video Clause 6.3 Property Name
freeBusyStatus
Context
Event, Task
Change Controller
IETF
Initial Contents
Table 6 — JSCalendar Enum Values for freeBusyStatus (Context: Event, Task)
Enum Value Reference or Description free Clause 6.5.2 busy Clause 6.5.2 Property Name
kind
Context
Participant
Change Controller
IETF
Initial Contents
Table 7 — JSCalendar Enum Values for kind (Context: Participant)
Enum Value Reference or Description individual Clause 6.5.9 group Clause 6.5.9 resource Clause 6.5.9 location Clause 6.5.9 Property Name
participationStatus
Context
Participant
Change Controller
IETF
Initial Contents
Table 8 — JSCalendar Enum Values for participationStatus (Context: Participant)
Enum Value Reference or Description needs-action Clause 6.5.9 accepted Clause 6.5.9 declined Clause 6.5.9 tentative Clause 6.5.9 delegated Clause 6.5.9 Property Name
privacy
Context
Event, Task
Change Controller
IETF
Initial Contents
Table 9 — JSCalendar Enum Values for privacy (Context: Event, Task)
Enum Value Reference or Description public Clause 6.5.3 private Clause 6.5.3 secret Clause 6.5.3 Property Name
progress
Context
Task, Participant
Change Controller
IETF
Initial Contents
Table 10 — JSCalendar Enum Values for progress (Context: Task, Participant)
Enum Value Reference or Description needs-action Clause 7.2.5 in-process Clause 7.2.5 completed Clause 7.2.5 failed Clause 7.2.5 cancelled Clause 7.2.5 Property Name
relation
Context
Relation
Change Controller
IETF
Initial Contents
Table 11 — JSCalendar Enum Values for relation (Context: Relation)
Enum Value Reference or Description first Relation next Relation child Relation parent Relation Property Name
relativeTo
Context
OffsetTrigger, Location
Change Controller
IETF
Initial Contents
Table 12 — JSCalendar Enum Values for relativeTo (Context: OffsetTrigger, Location)
Enum Value Reference or Description start Clause 6.6.2 end Clause 6.6.2 Property Name
roles
Context
Participant
Change Controller
IETF
Initial Contents
Table 13 — JSCalendar Enum Values for roles (Context: Participant)
Enum Value Reference or Description owner Clause 6.5.9 attendee Clause 6.5.9 optional Clause 6.5.9 informational Clause 6.5.9 chair Clause 6.5.9 contact Clause 6.5.9 Property Name
scheduleAgent
Context
Participant
Change Controller
IETF
Initial Contents
Table 14 — JSCalendar Enum Values for replyToScheduleAgent (Context: Event, Task) and scheduleAgent (Context: Participant)
Enum Value Reference or Description server Clause 6.5.9 client Clause 6.5.9 none Clause 6.5.9 Property Name
status
Context
Event
Change Controller
IETF
Initial Contents
Table 15 — JSCalendar Enum Values for status (Context: Event)
Enum Value Reference or Description confirmed Clause 7.1.3 cancelled Clause 7.1.3 tentative Clause 7.1.3
11. 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.
Bibliography
[1] ISO/IEC 9070:1991, International Organization for Standardization and International Electrotechnical Commission. Information technology — SGML support facilities — Registration procedures for public text owner identifiers. Second edition. 1991. Geneva. https://www.iso.org/standard/16645.html.
[2] IETF RFC 6376, D. CROCKER, T. HANSEN and M. KUCHERAWY (eds.). DomainKeys Identified Mail (DKIM) Signatures. 2011. RFC Publisher. https://www.rfc-editor.org/info/rfc6376.
[3] IETF RFC 7265, P. KEWISCH, C. DABOO and M. DOUGLASS. jCal: The JSON Format for iCalendar. 2014. RFC Publisher. https://www.rfc-editor.org/info/rfc7265.
[4] IETF RFC 7986, C. DABOO. New Properties for iCalendar. 2016. RFC Publisher. https://www.rfc-editor.org/info/rfc7986.
[5] LOCATIONTYPES, IANA, “Location Types Registry”, <https://www.iana.org/assignments/location-type-registry>.
[6] LINKRELS, IANA, “Link Relations: Link Relation Types”, <https://www.iana.org/assignments/link-relations>.
[7] MEDIATYPES, IANA, “Media Types”, <https://www.iana.org/assignments/media-types>.