Time Zone Data Distribution Service (tzdist)

Last modified: 2016-04-02

Chairs

Applications and Real-Time Area Advisor

Mailing Lists:

General Discussion: tzdist@ietf.org
To Subscribe: https://www.ietf.org/mailman/listinfo/tzdist
Archive: https://mailarchive.ietf.org/arch/browse/tzdist/

Description of Working Group:

The tzdist working group will define a time zone data distribution protocol that allows for efficient, timely updates of time zone data to be delivered to clients. The protocol must scale to vast numbers of clients, such as the potential "internet of things" devices, as well as to today's desktop computers and servers.

A time zone is a region that has a uniform local time for legal, commercial, and social purposes, with some regions using daylight saving time (DST) rules for part of the year. A local time is defined as a standard offset from Coordinated Universal Time (UTC), and a set of DST rules. Time zone data represents the history, current, and future local time rules for these regions, together with an associated time zoneidentifier.

Time zone data is a critical element of computer systems and devices that make use of local time. In particular, it is critical to any calendaring and scheduling system, such as iCalendar (RFC 5545). Daylight saving time rules, which affect local UTC offsets, can change - sometimes at very short notice (just a few days) - as those rules are typically defined by political processes. Currently, there is no efficient, fast way to ensure that time zone data is updated in a timely and reliable manner on devices that need it. Time zone changes are often delivered as operating system updates, and are thus tied to release schedules that can trail the actual time zone changes by a significant period of time. A service is needed that can provide timely, reliable updates.

One added benefit of such a service for iCalendar is the ability for calendaring clients and servers to agree on common, standard definitions of time zone data, removing the need to pass time zone data directly "by value" in iCalendar data. By allowing clients and servers to use time zones "by reference" significant network bandwidth and storage savings can be achieved.

This working group will:

- Define a time zone data distribution protocol that allows for efficient, timely updates of time zone data to be delivered to clients. This protocol must scale to vast numbers of clients, such as the potential "internet of things" devices, as well as to today's desktop computers and servers.

- Define an extension to CalDAV (RFC 4791) to allow clients and servers to use time zones "by reference" to improve the efficiency of the overall protocol.

The working group will use the following drafts as initial input for its work:

draft-douglass-timezone-service-11
draft-daboo-caldav-timezone-ref-01

The working group will work under the following parameters:

- The time zone data distribution protocol will initially be targeted at iCalendar-based clients, but should be flexible enough to deliver time zone data in other formats.

- The time zone data will be based on the Time Zone Database (http://www.iana.org/time-zones) but must be able to include any source of time zone data.

- The time zone data distribution protocol should also offer an API to allow thin clients to easily make use of time zone data by querying for UTC offsets, offloading the sometimes complex work of expanding recurrence rules to the service. This API should be extensible to support other types of time zone operations in the future.

- The time zone data distribution protocol will use current security protocols to protect the integrity and confidentiality of the data as it is distributed, and may also address these issues with respect to retrieval of data from its original source (such as the Time Zone Database). Even public time zone data can represent a significant privacy exposure when it is associated with the user or endpoint that is retrieving it.

The following are Out of scope for the working group:

- Any changes to the Time Zone Database process or infrastructure, as documented in RFC 6557. However, the WG may work with IANA in order to make integrity checking information, such as public keys, readily accessible for protocol use.

- The naming process for time zone identifiers. The working group can consider adding a mechanism, such as a "namespace" prefix, to differentiate different time zone sources, but the nature of the time zone identifiers used will be controlled by the sources themselves.

- Lookup protocols or APIs to map a location to a time zone.

Goals and Milestones

Done Request publication of CalDAV extension draft as Standards Track RFC
draft-ietf-tzdist-caldav-timezone-ref
Done WGLC for CalDAV extension draft
draft-ietf-tzdist-caldav-timezone-ref
Done Request publication of time zone data distribution protocol draft as Standards Track RFC
Done WGLC for time zone data distribution protocol draft
draft-ietf-tzdist-service
Done Adopt a CalDAV extension draft as WG document
Done Adopt time zone data distribution protocol as WG document

Request for Comments

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