Time Zone Data Distribution Service
Time Zone Data Distribution Service WG
||Time Zone Data Distribution Service
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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 zone
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,
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
The working group will use the following drafts as initial input for its
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.