Time Zone Data Distribution Service
RFC 7808

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Internet Engineering Task Force (IETF)                       M. Douglass
Request for Comments: 7808                           Spherical Cow Group
Category: Standards Track                                       C. Daboo
ISSN: 2070-1721                                                    Apple
                                                              March 2016

                  Time Zone Data Distribution Service

Abstract

   This document defines a time zone data distribution service that
   allows reliable, secure, and fast delivery of time zone data and
   leap-second rules to client systems such as calendaring and
   scheduling applications or operating systems.

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 5741.

   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/rfc7808.

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.

Douglass & Daboo             Standards Track                    [Page 1]
RFC 7808                     TZDIST Service                   March 2016

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Conventions . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Architectural Overview  . . . . . . . . . . . . . . . . . . .   5
   3.  General Considerations  . . . . . . . . . . . . . . . . . . .   7
     3.1.  Time Zone . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.2.  Time Zone Data  . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Time Zone Metadata  . . . . . . . . . . . . . . . . . . .   7
     3.4.  Time Zone Data Server . . . . . . . . . . . . . . . . . .   7
     3.5.  Observance  . . . . . . . . . . . . . . . . . . . . . . .   7
     3.6.  Time Zone Identifiers . . . . . . . . . . . . . . . . . .   7
     3.7.  Time Zone Aliases . . . . . . . . . . . . . . . . . . . .   8
     3.8.  Time Zone Localized Names . . . . . . . . . . . . . . . .   8
     3.9.  Truncating Time Zones . . . . . . . . . . . . . . . . . .   9
     3.10. Time Zone Versions  . . . . . . . . . . . . . . . . . . .  10
   4.  Time Zone Data Distribution Service Protocol  . . . . . . . .  10
     4.1.  Server Protocol . . . . . . . . . . . . . . . . . . . . .  10
       4.1.1.  Time Zone Queries . . . . . . . . . . . . . . . . . .  11
       4.1.2.  Time Zone Formats . . . . . . . . . . . . . . . . . .  11
       4.1.3.  Time Zone Localization  . . . . . . . . . . . . . . .  12
       4.1.4.  Conditional Time Zone Requests  . . . . . . . . . . .  12
       4.1.5.  Expanded Time Zone Data . . . . . . . . . . . . . . .  14
       4.1.6.  Server Requirements . . . . . . . . . . . . . . . . .  14
       4.1.7.  Error Responses . . . . . . . . . . . . . . . . . . .  14
       4.1.8.  Extensions  . . . . . . . . . . . . . . . . . . . . .  14
     4.2.  Client Guidelines . . . . . . . . . . . . . . . . . . . .  14
       4.2.1.  Discovery . . . . . . . . . . . . . . . . . . . . . .  14
         4.2.1.1.  SRV Service Labels for the Time Zone Data
                   Distribution Service  . . . . . . . . . . . . . .  15
         4.2.1.2.  TXT Records for a Time Zone Data Distribution
                   Service . . . . . . . . . . . . . . . . . . . . .  15
         4.2.1.3.  Well-Known URI for a Time Zone Data Distribution
                   Service . . . . . . . . . . . . . . . . . . . . .  16
           4.2.1.3.1.  Example: Well-Known URI Redirects to Actual
                       Context Path  . . . . . . . . . . . . . . . .  17
       4.2.2.  Synchronization of Time Zones . . . . . . . . . . . .  17
         4.2.2.1.  Initial Synchronization of All Time Zones . . . .  17
         4.2.2.2.  Subsequent Synchronization of All Time Zones  . .  17
         4.2.2.3.  Synchronization with Preexisting Time Zone Data .  18
   5.  Actions . . . . . . . . . . . . . . . . . . . . . . . . . . .  18
     5.1.  "capabilities" Action . . . . . . . . . . . . . . . . . .  18