iCalendar Format Extensions for JSCalendar
draft-stepanek-icalendar-jscalendar-extensions-00
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|---|---|---|---|
| Author | Robert Stepanek | ||
| Last updated | 2025-05-13 | ||
| Replaced by | draft-ietf-calext-icalendar-jscalendar-extensions | ||
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draft-stepanek-icalendar-jscalendar-extensions-00
calext R. Stepanek
Internet-Draft Fastmail
Intended status: Standards Track 13 May 2025
Expires: 14 November 2025
iCalendar Format Extensions for JSCalendar
draft-stepanek-icalendar-jscalendar-extensions-00
Abstract
This document defines a set of new elements for iCalendar and extends
the use of existing ones. Their main purpose is to extend the
semantics of iCalendar with elements defined in JSCalendar, but the
new definitions also aim to be useful within just the iCalendar
format. This document updates RFC 5545 ("Internet Calendaring and
Scheduling Core Object Specification (iCalendar)").
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 14 November 2025.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 2
1.2. ABNF Notations . . . . . . . . . . . . . . . . . . . . . 3
2. Updated Properties . . . . . . . . . . . . . . . . . . . . . 3
2.1. GEO Property . . . . . . . . . . . . . . . . . . . . . . 3
3. New Properties . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. DIGEST Property . . . . . . . . . . . . . . . . . . . . . 4
3.2. SHOW-WITHOUT-TIME Property . . . . . . . . . . . . . . . 5
3.3. URI Property . . . . . . . . . . . . . . . . . . . . . . 7
4. New Parameters . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. HASH Parameter . . . . . . . . . . . . . . . . . . . . . 8
5. New Components . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. VCONFERENCE Component . . . . . . . . . . . . . . . . . . 9
5.2. VLOCALIZATION Component . . . . . . . . . . . . . . . . . 11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Normative References . . . . . . . . . . . . . . . . . . 13
9. Informative References . . . . . . . . . . . . . . . . . . . 14
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 15
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
The JSCalendar [I-D.stepanek-jscalendarbis] format aims to be an
alternative to the iCalendar [RFC5545] format for representation of
calendaring data. As such, it introduces new semantics that are not
covered in the current definition of iCalendar and its various
extensions. Converting calendaring data between the two formats is
defined in [I-D.ietf-calext-jscalendar-icalendar] with the goal of
not losing any semantics during conversion. To achieve this, this
document defines new elements iCalendar and extends existing
definitions. Doing so, it follows the recommendations for
introducing new iCalendar elements as specified in Section 3 of
[RFC7986].
1.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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1.2. ABNF Notations
The ABNF definitions in this document use the notations of [RFC5234].
ABNF rules not defined in this document are defined in either
[RFC5234] (such as the ABNF for CRLF, WSP, DQUOTE, VCHAR, ALPHA, and
DIGIT) or [RFC5545].
2. Updated Properties
2.1. GEO Property
This specification modifies the definition of the "GEO" property to
also allow "geo" URI values [RFC5870] as property values. The
following additions are made to the definition of this property,
originally specified in Section 3.8.1.6 of [RFC5545]:
Value Type (replaces original): The default value type for this
property is FLOAT, the value MUST be two SEMICOLON-separated FLOAT
values. The value type can also be set to URI, in which case the
VALUE parameter MUST be set.
Description (in addition to original): A Uniform Resource Identifier
for Geographic Locations ("geo" URI) allows for richer semantics
than the FLOAT value, such as defining geographic altitude,
location uncertainty or the coordinate's reference system. The
GEO property value MAY be of type URI to contain such coordinates.
Property values of type URI MUST be valid according to the "geo"
URI scheme syntax defined in Section 3.3 of [RFC5870].
Format Definition (replaces original):
geo = geofloat / geouri
geofloat = "GEO" geoparam ":" geovalue CRLF
geoparam = *(";" other-param)
;Latitude and Longitude components
geovalue = float ";" float
geouri = "GEO" geouriparam ":" uri CRLF
geouriparam = *(
;
; The following is REQUIRED,
; but MUST NOT occur more than once.
;
(";" "VALUE" "=" "URI") /
;
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; The following is OPTIONAL,
; and MAY occur more than once.
;
(";" other-param)
;
)
Example(s): The following are examples of this property:
GEO:37.386013;-122.082932
GEO;VALUE=URI:geo:48.198634,16.371648;crs=wgs84;u=40
3. New Properties
3.1. DIGEST Property
Property Name: DIGEST
Purpose: To represent the result of a hash function or a checksum.
Value Type: TEXT
Property Parameters: The "HASH" parameter (Section 4.1) MUST be
specified exactly once on this property. The "LANGUAGE" parameter
MUST NOT be specified on this property. Other IANA and non-
standard parameters MAY be specified on this property.
Conformance: This property can be specified once in a
"VLOCALIZATION" calendar component.
Description: This property represents the result of a hash function
or checksum algorithm. The semantics and purpose of its property
value MUST be defined for each calendar component which allows to
specify the "DIGEST" property. See the definition of the
"VLOCALIZATION" component (Section 5.2) for an example.
This document defines the "Property Set Digest", which is the
result of applying the hash function specified in the "HASH"
parameter to a set of iCalendar properties. This digest is
created as follows, all strings MUST be UTF-8 encoded and in
Unicode Normalization Form NFC [UNorm]:
1. For each property in the set, reorder its parameters in
ascending order by comparing its parameter names, breaking
ties by parameter value. Parameter names and parameter values
in form "paramtext" compare in uppercase, parameter values in
form "quoted-string" compare case-sensitively.
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2. For each sorted property, generate an unfolded content line.
Every content line ends with the CRLF sequence.
3. Sort the resulting content line strings in ascending order,
then concatenate them to a single string, preserving their
CRLF endings.
4. Apply the hash function to the string and set the result as
the "DIGEST" property value.
The Property Set Digest can produce different digests for property
sets that are semantically equivalent. This is because it does
not enforce setting or removing default parameter values, or the
"VALUE" parameter, or applying any other iCalendar-specific
normalization. As a result, differing digests only indicate that
_something_ changed in the property set, but if this change is
significant depends on the semantics of the calendar component
that specifies using the "DIGEST" property.
Format Definition:
digest = "DIGEST" digestparam ":" TEXT CRLF
digestparam = *(
;
; The following is REQUIRED,
; but MUST NOT occur more than once.
;
(";" hashparam )
;
; The following is OPTIONAL,
; and MAY occur more than once.
;
(";" other-param)
;
)
Example:
DIGEST;HASH=MD5:a16d6a19dd1d5c3baf591276eff96433
3.2. SHOW-WITHOUT-TIME Property
Property Name: SHOW-WITHOUT-TIME
Purpose: To indicate that the exact time span is not important when
displaying this calendar object.
Value Type: BOOLEAN -- no default
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Property Parameters: IANA and non-standard parameters can be
specified on this property.
Conformance: This property can be specified once in a "VEVENT" or
"VTODO" calendar component.
Description: This indicates that the exact time span 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, but in contrast to a DATE value is limited to a specific
time zone or business hours. While the time component is
important for free-busy calculations and checking for scheduling
clashes, calendars may choose to display it as an all-day event
and/or display the object separately to other objects to enhance
the user's view of their schedule.
This property only is for presentation purposes, it does not have
any impact on the temporal characteristics of a calendar object.
This property MAY be specified on VEVENT components where the
DTSTART property is of type DATE-TIME, or in VTODO components
where either the DTSTART or DUE property is specified and has type
DATE-TIME. In all other cases it MUST NOT be set. If this
property is set, its property value MUST be "TRUE", e.g. it MUST
be omitted rather than having value "FALSE".
Implementations that are unaware of the "SHOW-WITHOUT-TIME"
property might inadvertently preserve this property when changing
a calendar object's temporal type from DATE-TIME to DATE.
Implementations SHOULD therefore ignore rather than reject the
incorrectly specified SHOW-WITHOUT-TIME property. They MUST NOT
preserve the ill-specified property in the calendaring data.
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Format Definition:
showwt = "SHOW-WITHOUT-TIME" showwtparam ":" "TRUE" CRLF
showwtparam = *(
;
; The following is REQUIRED,
; but MUST NOT occur more than once.
;
(";" "VALUE" "=" "BOOLEAN") /
;
; The following is OPTIONAL,
; and MAY occur more than once.
;
(";" other-param)
;
)
Example:
SHOW-WITHOUT-TIME;VALUE=BOOLEAN:TRUE
3.3. URI Property
Property Name: URI
Purpose: To associate a Uniform Resource Identifier (URI) with a
calendar component.
Value Type: URI -- no default
Property Parameters: The "LANGUAGE" parameter MUST NOT be specified
on this property. Other IANA and non-standard parameters can be
specified on this property.
Conformance: This property can be specified once in a "VCONFERENCE"
calendar component.
Description: This property associates a Uniform Resource Identifier
[RFC3986] with a calendar component. In contrast to the "UID"
property, which defines its values to be of type TEXT, this
property requires its value to be a syntactically valid URI. In
contrast to the "URL" property, this property neither provides a
dynamic rendition of the associated calendar component, nor does
it _locate_ a resource - it only identifies the calendar
component.
The semantics and purpose of this identifier MUST be defined for
each calendar component containing the "URI" property. This
document defines the semantics of the "URI" property for the
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"VCONFERENCE" component. Similarly, future iCalendar extensions
might consider using the "URI" property in cases where associating
calendaring data by use of the "UID" and "RELATED-TO" properties
is not possible.
Format Definition:
uriprop = "URI" uriparam ":" uri CRLF
uriparam = *(
;
; The following is REQUIRED,
; but MUST NOT occur more than once.
;
(";" "VALUE" "=" "URI") /
;
; The following is OPTIONAL,
; and MAY occur more than once.
;
(";" other-param)
;
)
Example:
URI;VALUE=URI:urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6
4. New Parameters
4.1. HASH Parameter
Parameter Name: HASH
Purpose: To specify a hash function for a hash digest.
Description: In context of the "DIGEST" property, this parameter
specifies the hash function that was used to create the property
value. Any parameter value is allowed, it is not an enumerated
value to allow future parameter values incorporate parameters for
hash functions. The same case sensitivity as for other parameters
value applies: "paramtext" values are case-insensitive, "quoted-
string" values are case-sensitive. This document defines the
semantics for the following parameter value:
Parameter Value: MD5 (case-insensitive)
Description This produces the MD5 Message-Digest [RFC1321] from
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its input string. This hash MUST NOT be used for cryptographic
purposes and the security considerations of [RFC6151] apply.
The result of this hash is hex-encoded with all characters in
lowercase.
Format Definition:
hashparam = "HASH" "=" param-value *("," param-value)
Example:
DIGEST;HASH=MD5:a16d6a19dd1d5c3baf591276eff96433
5. New Components
5.1. VCONFERENCE Component
Component Name: VCONFERENCE
Purpose: This component provides additional information about a
virtual conference specified in the CONFERENCE property [RFC7986]
(Section 5.11).
Conformance: This component can be specified multiple times in any
component that allows to specify the "CONFERENCE" property.
Description: This component augments information provided by the
"CONFERENCE" property for a virtual meeting or conference.
Specifically, this specification adds support for long-form plain
text and rich-text descriptions, which can not feasibly be
provided in the "LABEL" parameter of the "CONFERENCE" property.
A "VCONFERENCE" component by itself does not represent a virtual
meeting and it does not replace information provided by the
"CONFERENCE" property. Instead, a calendar component that
specifies the "VCONFERENCE" component MUST also specify a
"CONFERENCE" property, and that "CONFERENCE" property value MUST
match the value of the "URI" property (Section 3.3) specified in
the "VCONFERENCE" component. The URI values MUST be equal
character strings, as specified in Section 6 of [RFC3986].
A "VCONFERENCE" component MAY contain one "DESCRIPTION" property
and multiple "STYLED-DESCRIPTION" properties, but one of them MUST
NOT specify the "DERIVED" parameter and all others MUST specify
the "DERIVED" parameter (e.g. it must have one and only one non-
derived description). For future extensibility, this
specification does not define the "DESCRIPTION" or "STYLED-
DESCRIPTION" properties to be mandatory, but a "VCONFERENCE"
component MUST contain at least one property other than the "URI"
property.
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Implementations that are unaware of the "VCONFERENCE" component
might inadvertently preserve this component when removing its
related "CONFERENCE" property from the calendar object. Changing
the URI value of the "CONFERENCE" property is in this context
considered a removal followed by inserting a new element.
Implementations SHOULD therefore ignore rather than reject such
incorrectly specified "VCONFERENCE" components. They MUST NOT
preserve the ill-specified component in the calendaring data.
Format Definition:
vconfc = "BEGIN" ":" "VCONFERENCE" CRLF
*(
;
; The following are REQUIRED,
; but MUST NOT occur more than once.
;
uriprop /
;
; The following are OPTIONAL,
; but MUST NOT occur more than once.
;
description /
;
; The following are OPTIONAL,
; and MAY occur more than once
;
styleddescription
;
;
; The following are OPTIONAL,
; and MAY occur more than once.
;
x-prop / iana-prop
;
)
"END" ":" "VCONFERENCE" CRLF
Example(s): The following is an example of this component:
BEGIN:VCONFERENCE
URI;VALUE=URI:https://chat.example.com/x?id=123456
DESCRIPTION:This is the first in a series of sessions:\n
...
END:VCONFERENCE
CONFERENCE;VALUE=URI;FEATURE=AUDIO,VIDEO;
LABEL=Product Brainstorming Session:https://chat.example.com/x?id=123456
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5.2. VLOCALIZATION Component
Component Name: VLOCALIZATION
Purpose: To provide internationalized and localized alternate text
representations of calendar component elements.
Conformance: This component can be specified multiple times in any
component that allows to specify at least one property with the
"LANGUAGE" parameter.
Description: This component provides internationalized and localized
alternate text representations of properties specified in a
calendar component. Its main purpose is for use with descriptive
elements such as the "SUMMARY" or "DESCRIPTION" properties, but it
MAY be used with any property on which the "LANGUAGE" parameter
can be set.
A "VLOCALIZATION" component MUST contain one or more properties
which each MUST specify exactly once the "LANGUAGE" parameter.
The "LANGUAGE" parameter values MAY differ between properties.
The component MUST specify the "URI" property (Section 3.3)
exactly once. A calendar component that contains the
"VLOCALIZATION" component is then localized to a specific human
language by replacing all its properties where the "ALTREP"
parameter value matches the "URI" property value of the
"VLOCALIZATION" with those properties in the "VLOCALIZATION"
component, for which the "LANGUAGE" parameter value matches the
language tag of the target human language.
The localized calendar component MUST be valid, e.g. mandatory
properties MUST be set. The URI values of the "ALTREP" parameter
and "URI" property MUST be compared as character strings, as
specified in Section 6 of [RFC3986]. The URI value MUST be a
valid URI in the "urn" scheme [RFC8141] with namespace identifier
"uuid" [RFC9562].
The "VLOCALIZATION" component SHOULD only contain properties for
which a property of the same name also is specified in the non-
localized component, e.g. a "VLOCALIZATION" component is only
meant to provide alternate text representations, not to add new
content.
Implementations that are unaware of the "VLOCALIZATION" component
might change property values in the non-localized component,
inadvertently invalidating the contents of the localized
properties. To mitigate this, implementations MUST specify the
"DIGEST" (Section 3.1) property at least once in the
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"VLOCALIZATION" component. The property value MUST be the
"Property Set Digest" as defined in Section 3.1, where the
property set consists of all those properties in the non-localized
component, for which the "ALTREP" parameter value matches the
"URI" property value of the "VLOCALIZATION" component. The
"ALTREP" parameter is part of the hashed property. Multiple
"DIGEST" properties MUST each specify a different "HASH" parameter
value.
Implementations MUST consider a "VLOCALIZATION" component as
outdated, if the "DIGEST" property value does not match the
expected digest. How to handle outdated localizations is
implementation-specific, but implementations MUST not preserve
"VLOCALIZATION" components with outdated "DIGEST" property values.
Format Definition:
vlocalizationc = "BEGIN" ":" "VLOCALIZATION" CRLF
*(
;
; The following is REQUIRED,
; but MUST NOT occur more than once.
;
uriprop
;
; The following is REQUIRED,
; and MAY occur more than once.
; "HASH" parameter values MUST differ.
;
digest
;
; The following are OPTIONAL,
; and MAY occur more than once.
; At least one MUST have the
; "LANGUAGE" parameter set.
;
x-prop / iana-prop
;
)
"END" ":" "VLOCALIZATION" CRLF
Example(s): The following is an example of this component:
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DTSTART;VALUE=DATE:20250701
SUMMARY;LANGUAGE="en-ca"
;ALTREP="urn:uuid:cd92c017-f7b0-4ac1-a852-c1d28ab172e5"
:Canada Day
DESCRIPTION;LANGUAGE="en-ca"
;ALTREP="urn:uuid:cd92c017-f7b0-4ac1-a852-c1d28ab172e5"
:Canada Day celebrates the anniversary of Canadian Confederation
which occurred on July 1, 1867.
BEGIN:VLOCALIZATION
URI;VALUE=URI:urn:uuid:cd92c017-f7b0-4ac1-a852-c1d28ab172e5
DIGEST;HASH=MD5:863f0708251b33990b43830a8ca754e4
SUMMARY;LANGUAGE="fr-ca"
:Fête du Canada
DESCRIPTION;LANGUAGE="fr-ca"
:La Fête du Canada est un jour férié commémorant la date de
formation du Canada le 1er juillet 1867.
END:VLOCALIZATION
6. Security Considerations
This specification extends [RFC5545]. The same security
considerations as outlined in Section 7 of [RFC5545] apply. In
addition, Section 4.1 refers to the security considerations of the
MD5 Message-Digest Algorithm.
7. IANA Considerations
TBD
8. References
8.1. Normative References
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
DOI 10.17487/RFC1321, April 1992,
<https://www.rfc-editor.org/info/rfc1321>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
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[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and
Scheduling Core Object Specification (iCalendar)",
RFC 5545, DOI 10.17487/RFC5545, September 2009,
<https://www.rfc-editor.org/info/rfc5545>.
[RFC5870] Mayrhofer, A. and C. Spanring, "A Uniform Resource
Identifier for Geographic Locations ('geo' URI)",
RFC 5870, DOI 10.17487/RFC5870, June 2010,
<https://www.rfc-editor.org/info/rfc5870>.
[RFC6151] Turner, S. and L. Chen, "Updated Security Considerations
for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
RFC 6151, DOI 10.17487/RFC6151, March 2011,
<https://www.rfc-editor.org/info/rfc6151>.
[RFC7986] Daboo, C., "New Properties for iCalendar", RFC 7986,
DOI 10.17487/RFC7986, October 2016,
<https://www.rfc-editor.org/info/rfc7986>.
[RFC8141] Saint-Andre, P. and J. Klensin, "Uniform Resource Names
(URNs)", RFC 8141, DOI 10.17487/RFC8141, April 2017,
<https://www.rfc-editor.org/info/rfc8141>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC9562] Davis, K., Peabody, B., and P. Leach, "Universally Unique
IDentifiers (UUIDs)", RFC 9562, DOI 10.17487/RFC9562, May
2024, <https://www.rfc-editor.org/info/rfc9562>.
9. Informative References
[I-D.ietf-calext-jscalendar-icalendar]
Stepanek, R., "JSCalendar: Converting from and to
iCalendar", Work in Progress, Internet-Draft, draft-ietf-
calext-jscalendar-icalendar, 12 May 2025,
<https://datatracker.ietf.org/doc/draft-ietf-calext-
jscalendar-icalendar/>.
[I-D.stepanek-jscalendarbis]
Jenkins, N.M. and R. Stepanek, "JSCalendar: A JSON
Representation of Calendar Data", Work in Progress,
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Internet-Draft, draft-stepanek-jscalendarbis, 12 May 2025,
<https://datatracker.ietf.org/doc/draft-stepanek-
jscalendarbis/>.
[UNorm] UTS #15, Unicode Normalization Forms,
<https://www.unicode.org/reports/tr15/>.
Acknowledgments
The descriptions of Canada Day in the example in Section 5.2 were
copied from the English Wikipedia website
(https://en.wikipedia.org/wiki/Canada_Day) which makes the text
available under the Creative Commons Attribution-ShareAlike 4.0
License (https://en.wikipedia.org/wiki/
Wikipedia:Text_of_the_Creative_Commons_Attribution-
ShareAlike_4.0_International_License).
Author's Address
Robert Stepanek
Fastmail
PO Box 234
Collins St. West
Melbourne VIC 8007
Australia
Email: rsto@fastmailteam.com
Stepanek Expires 14 November 2025 [Page 15]