draft-ietf-calext-rscale-02.txt   draft-ietf-calext-rscale-03.txt 
Network Working Group C. Daboo Network Working Group C. Daboo
Internet-Draft Apple Inc. Internet-Draft Apple Inc.
Updates: 4791, 5545, 5546, 6321, 7265 G. Yakushev Updates: 5545, 6321, 7265 (if approved) G. Yakushev
(if approved) Google Inc. Intended status: Standards Track Google Inc.
Intended status: Standards Track December 10, 2014 Expires: July 11, 2015 January 7, 2015
Expires: June 13, 2015
Non-Gregorian Recurrence Rules in iCalendar Non-Gregorian Recurrence Rules in iCalendar
draft-ietf-calext-rscale-02 draft-ietf-calext-rscale-03
Abstract Abstract
This document defines how non-Gregorian recurrence rules can be This document defines extensions to iCalendar (RFC 5545) to support
specified and used in iCalendar data, and with CalDAV servers. use of non-Gregorian recurrence rules. It also defines how CalDAV
(RFC 4791) servers and clients can be extended to support these new
recurrence rules.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on June 13, 2015. This Internet-Draft will expire on July 11, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Extended RRULE Property . . . . . . . . . . . . . . . . . . . 5 4. Extended RRULE Property . . . . . . . . . . . . . . . . . . . 6
4.1. Handling Leap Months . . . . . . . . . . . . . . . . . . 6 4.1. Handling Leap Months . . . . . . . . . . . . . . . . . . 7
4.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 7 4.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Registering Calendar Systems . . . . . . . . . . . . . . . . 9 5. Registering Calendar Systems . . . . . . . . . . . . . . . . 10
6. Use with iTIP . . . . . . . . . . . . . . . . . . . . . . . . 10 6. Use with iTIP . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Use with xCal . . . . . . . . . . . . . . . . . . . . . . . . 11 7. Use with xCal . . . . . . . . . . . . . . . . . . . . . . . . 11
8. Use with jCal . . . . . . . . . . . . . . . . . . . . . . . . 11 8. Use with jCal . . . . . . . . . . . . . . . . . . . . . . . . 12
9. Use with CalDAV . . . . . . . . . . . . . . . . . . . . . . . 12 9. Use with CalDAV . . . . . . . . . . . . . . . . . . . . . . . 13
9.1. CALDAV:supported-rscale-set Property . . . . . . . . . . 13 9.1. CALDAV:supported-rscale-set Property . . . . . . . . . . 13
10. Security Considerations . . . . . . . . . . . . . . . . . . . 14 10. Security Considerations . . . . . . . . . . . . . . . . . . . 14
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
13.1. Normative References . . . . . . . . . . . . . . . . . . 14 13.1. Normative References . . . . . . . . . . . . . . . . . . 14
13.2. Informative References . . . . . . . . . . . . . . . . . 15 13.2. Informative References . . . . . . . . . . . . . . . . . 15
Appendix A. Change History (To be removed by RFC Editor before Appendix A. Change History (To be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 15 publication) . . . . . . . . . . . . . . . . . . . . 15
Appendix B. xCal RELAX NG schema update . . . . . . . . . . . . 16 Appendix B. xCal RELAX NG schema update . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
The iCalendar [RFC5545] data format is in widespread use to represent The iCalendar [RFC5545] data format is in widespread use to represent
calendar data. iCalendar represents dates and times using the calendar data. iCalendar represents dates and times using the
Gregorian calendar system only. It does provide a way to use non- Gregorian calendar system only. It does provide a way to use non-
Gregorian calendar systems via a "CALSCALE" property, but this has Gregorian calendar systems via a "CALSCALE" property, but this has
never been used. However, there is a need to support at least non- never been used. However, there is a need to support at least non-
Gregorian recurrence patterns to cover anniversaries, and many local, Gregorian recurrence patterns to cover anniversaries, and many local,
religious, or civil holidays based on non-Gregorian dates. religious, or civil holidays based on non-Gregorian dates.
skipping to change at page 2, line 51 skipping to change at page 2, line 51
property in iCalendar for implementing non-Gregorian calendars: property in iCalendar for implementing non-Gregorian calendars:
1. The "CALSCALE" property exists in the top-level "VCALENDAR" 1. The "CALSCALE" property exists in the top-level "VCALENDAR"
objects and thus applies to all components within that object. objects and thus applies to all components within that object.
In today's multi-cultural society, that restricts the ability to In today's multi-cultural society, that restricts the ability to
mix events from different calendar systems within the same mix events from different calendar systems within the same
iCalendar object. e.g., it would prevent having both the iCalendar object. e.g., it would prevent having both the
Gregorian New Year and Chinese New Year in the same iCalendar Gregorian New Year and Chinese New Year in the same iCalendar
object. object.
2. Many countries observe daylight savings time, encoded in 2. Time zone and daylight saving time rules are typically published
iCalendar using the "VTIMEZONE" component. Time zone and using Gregorian calendar dates and rules (e.g., "the 3rd Sunday
daylight saving time rules are always specified via Gregorian in March"), and thus converted to iCalendar "VTIMEZONE"
calendar based recurrence rules (e.g., "the 3rd Sunday in components using Gregorian date-time values and recurrence rules.
March"). This is problematic for non-Gregorian uses of This results in the problem whereby one component (the
"CALSCALE" which would by default also apply to the dates and "VTIMEZONE") is fixed to the Gregorian calendar system, and
rules used in the "VTIMEZONE" components in the corresponding another (a "VEVENT") wants to use a different non-Gregorian
iCalendar object. calendar scale, and thus the single top-level "CALSCALE" property
is again inadequate.
This specification solves these issues by allowing the "CALSCALE" to This specification solves these issues by allowing the "CALSCALE" to
remain set to Gregorian, but re-defining the recurrence rule property remain set to Gregorian, but re-defining the "RRULE" recurrence rule
"RRULE" to accept new items including one that allows non-Gregorian property to accept new items including one that allows non-Gregorian
calendar systems to be used. With this, all the date, time and calendar systems to be used. With this, all the date, time and
period values in the iCalendar object would remain specified using period values in the iCalendar object would remain specified using
the Gregorian calendar system, but repeating patterns in other the Gregorian calendar system, but repeating patterns in other
calendar systems could be defined. It is then up to calendar user calendar systems could be defined. It is then up to calendar user
agents and servers to map between Gregorian and non-Gregorian agents and servers to map between Gregorian and non-Gregorian
calendar systems in order to expand out recurrence instances. calendar systems in order to expand out recurrence instances. The
non-Gregorian recurrence rules can be used in any iCalendar component
that allows the "RRULE" property to be specified, including
"VTIMEZONE" components (to allow for possible future use of non-
Gregorian rules in published daylight saving time data).
This specification does not itself define calendar systems, rather it This specification does not itself define calendar systems, rather it
utilizes the calendar system registry defined by the Unicode utilizes the calendar system registry defined by the Unicode
Consortium in their CLDR (Common Locale Data Repository) project Consortium in their CLDR (Common Locale Data Repository) project
[UNICODE.CLDR], as implemented in the Unicode (ICU) Library [UNICODE.CLDR], as implemented in the Unicode (ICU) Library
[UNICODE.ICU]. [UNICODE.ICU].
This specification makes the following updates:
It updates iCalendar [RFC5545], xCal [RFC6321], and jCal
[RFC7265], to extend the "RRULE" property definition.
It updates iTIP [RFC5546] to specify how the extended "RRULE"
property should be handled in iTIP messages.
It updates CalDAV [RFC4791] to specify how the extended "RRULE"
property can be supported by CalDAV servers and clients.
2. Conventions Used in This Document 2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[RFC2119]. [RFC2119].
The notation used in this memo is the ABNF notation of [RFC5234] as The notation used in this memo is the ABNF notation of [RFC5234] as
used by iCalendar [RFC5545]. Any syntax elements shown below that used by iCalendar [RFC5545]. Any syntax elements shown below that
are not explicitly defined in this specification come from iCalendar are not explicitly defined in this specification come from iCalendar
skipping to change at page 14, line 17 skipping to change at page 14, line 37
This specification does not introduce any addition security concerns This specification does not introduce any addition security concerns
beyond those described in [RFC5545], [RFC5546], and [RFC4791]. beyond those described in [RFC5545], [RFC5546], and [RFC4791].
11. IANA Considerations 11. IANA Considerations
This document requires no IANA actions. This document requires no IANA actions.
12. Acknowledgments 12. Acknowledgments
Thanks to the following for feedback: Mark Davis, Mike Douglass, Thanks to the following for feedback: Mark Davis, Mike Douglass,
Peter Edberg, Marten Gajda, Philipp Kewisch, Ken Murchison, Arnaud Donald Eastlake, Peter Edberg, Marten Gajda, Philipp Kewisch,
Quillaud, Dave Thewlis, and Umaoka Yoshito. Jonathan Lennox, Ken Murchison, Arnaud Quillaud, Dave Thewlis, and
Umaoka Yoshito.
This specification originated from work at the Calendaring and This specification originated from work at the Calendaring and
Scheduling Consortium, which has helped with the development and Scheduling Consortium, which has helped with the development and
testing of implementations. testing of implementations.
13. References 13. References
13.1. Normative References 13.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
skipping to change at page 15, line 28 skipping to change at page 15, line 49
- Representation of dates and times", ISO Standard 8601, - Representation of dates and times", ISO Standard 8601,
2004. 2004.
[UNICODE.ICU] [UNICODE.ICU]
"International Components for Unicode", Unicode Consortium "International Components for Unicode", Unicode Consortium
ICU, April 2014, <http://site.icu-project.org>. ICU, April 2014, <http://site.icu-project.org>.
Appendix A. Change History (To be removed by RFC Editor before Appendix A. Change History (To be removed by RFC Editor before
publication) publication)
Changes in draft-ietf-calext-rscale-03:
1. Reworded abstract.
2. Added list of changes to other specs in Section 1.
3. Clarified behavior wrt VTIMEZONE in Section 1.
Changes in draft-ietf-calext-rscale-02: Changes in draft-ietf-calext-rscale-02:
1. Added xCal and jCal changes sections and relax NG schema 1. Added xCal and jCal changes sections and relax NG schema
appendix. appendix.
2. Added ICU reference at the end of Section 1. 2. Added ICU reference at the end of Section 1.
Changes in draft-ietf-calext-rscale-01: Changes in draft-ietf-calext-rscale-01:
1. Editorial changes/fixes per document shepherd review. 1. Editorial changes/fixes per document shepherd review.
 End of changes. 15 change blocks. 
29 lines changed or deleted 55 lines changed or added

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