Calendar Availability
RFC 7953

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Internet Engineering Task Force (IETF)                          C. Daboo
Request for Comments: 7953                                         Apple
Updates: 4791, 5545, 6638                                    M. Douglass
Category: Standards Track                            Spherical Cow Group
ISSN: 2070-1721                                              August 2016

                         Calendar Availability

Abstract

   This document specifies a new iCalendar (RFC 5545) component that
   allows the publication of available and unavailable time periods
   associated with a calendar user.  This component can be used in
   standard iCalendar free-busy lookups, including the iCalendar
   Transport-independent Interoperability Protocol (iTIP; RFC 5546)
   free-busy requests, to generate repeating blocks of available or busy
   time with exceptions as needed.

   This document also defines extensions to the Calendaring Extensions
   to WebDAV (CalDAV) calendar access protocol (RFC 4791) and the
   associated scheduling protocol (RFC 6638) to specify how this new
   calendar component can be used when evaluating free-busy time.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7953.

Daboo & Douglass             Standards Track                    [Page 1]
RFC 7953                  Calendar Availability              August 2016

Copyright Notice

   Copyright (c) 2016 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   3
   3.  iCalendar Extensions  . . . . . . . . . . . . . . . . . . . .   4
     3.1.  VAVAILABILITY Component . . . . . . . . . . . . . . . . .   4
     3.2.  Busy Time Type  . . . . . . . . . . . . . . . . . . . . .  10
   4.  Combining VAVAILABILITY Components  . . . . . . . . . . . . .  10
   5.  Calculating Free-Busy Time  . . . . . . . . . . . . . . . . .  12
     5.1.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  13
   6.  Use with iTIP . . . . . . . . . . . . . . . . . . . . . . . .  15
   7.  CalDAV Extensions . . . . . . . . . . . . . . . . . . . . . .  15
     7.1.  CalDAV Requirements Overview  . . . . . . . . . . . . . .  15
     7.2.  New Features in CalDAV  . . . . . . . . . . . . . . . . .  16
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  19
   9.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  19
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  20
     10.1.  Component Registrations  . . . . . . . . . . . . . . . .  20
     10.2.  Property Registrations . . . . . . . . . . . . . . . . .  20
   11. Normative References  . . . . . . . . . . . . . . . . . . . .  20
   Appendix A.  Example Calendar #1  . . . . . . . . . . . . . . . .  22
   Appendix B.  Example Calendar #2  . . . . . . . . . . . . . . . .  23
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  24
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  24

Daboo & Douglass             Standards Track                    [Page 2]
RFC 7953                  Calendar Availability              August 2016

1.  Introduction

   Calendar users often have regular periods of time when they are
   either available to be scheduled or always unavailable.  For example,
   an office worker will often wish only to appear free to their work
   colleagues during normal 'office hours' (e.g., Monday through Friday,
   9 am through 5 pm).  Or, a university professor might only be
   available to students during a set period of time (e.g., Thursday
   afternoons, 2 pm through 5 pm during term time only).  Ideally, users
   ought be able to specify such periods directly via their calendar
   user agent and have them automatically considered as part of the