Internet Engineering Task Force (IETF) E. Lear
Request for Comments: 6557 Cisco Systems GmbH
BCP: 175 P. Eggert
Category: Best Current Practice UCLA
ISSN: 2070-1721 February 2012
Procedures for Maintaining the Time Zone Database
Time zone information serves as a basic protocol element in
protocols, such as the calendaring suite and DHCP. The Time Zone
(TZ) Database specifies the indices used in various protocols, as
well as their semantic meanings, for all localities throughout the
world. This database has been meticulously maintained and
distributed free of charge by a group of volunteers, coordinated by a
single volunteer who is now planning to retire. This memo specifies
procedures involved with maintenance of the TZ database and
associated code, including how to submit proposed updates, how
decisions for inclusion of those updates are made, and the selection
of a designated expert by and for the time zone community. The
intent of this memo is, to the extent possible, to document existing
practice and provide a means to ease succession of the database
Status of This Memo
This memo documents an Internet Best Current Practice.
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
BCPs 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
Copyright (c) 2012 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
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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.
The IETF has specified several standards that make use of time zone
information. Time zone names are used in DHCP to configure devices
with correct local time [RFC4833]. Time zone names can appear in the
TZID field of calendaring VEVENTs [RFC5545]. The normative reference
for these values is the TZ Database [TZDB]. From the early 1980s
through 2011, that database, which has been in use on nearly all UNIX
systems, Java systems, and other sorts of systems, was hosted at the
U.S. National Institutes of Health (NIH). The database consists of
both historic and current entries for geographies throughout the
world. Associated with the database is a reference implementation of
ISO/IEC 9899 C [ISO9899C] and IEEE 1003.1 [IEEE1003.1] POSIX time
functions that can be used to convert time values.
The database was previously maintained by volunteers who participated
in the <email@example.com> mailing list that was also hosted at
the NIH. The database itself is updated approximately twenty times
per year, depending on the year, based on information these experts
provide to the maintainer. Arthur David Olson has maintained the
database, coordinated the mailing list, and provided a release
platform since the database's inception. With his retirement now
approaching, it is necessary to provide a means for this good work to
The time zone community has requested that the IETF adopt the ongoing
maintenance of the Time Zone Database. The time zone community would
like the IETF to maintain it in a consistent fashion to its
administration of the Internet protocol parameters and values.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
IANA (Internet Assigned Numbers Authority): For purposes of this
RFC, IANA is a role, not an organization. The IANA Considerations
defined in this RFC will be provided by the Internet Corporation
for Assigned Names and Numbers (ICANN) in accordance with the
IETF-ICANN "Memorandum of Understanding Concerning Technical Work
of the Internet Assigned Numbers Authority", which was signed and
ratified in March of 2000[RFC2860].
TZ Database: The Time Zone Database, sometimes referred to as the
"Olson Database". This database consists of information about
offsets from UTC for different localities, including daylight
saving time (DST) transition information.
TZ Coordinator: The person or people who maintain and manage release
of the TZ Database. The TZ Coordinator also has responsibility
for managing the TZ mailing list. The TZ Coordinator is an IANA
Designated Expert, as defined in Section 3.2 of [RFC5226], except
as regards to appeals, as discussed in Section 5 of this document.
Roughly speaking, this means that the IESG will choose one or more
experts to manage the TZ database, code, and mailing list. The TZ
Coordinator will also lead work to develop appropriate service
metrics. There SHALL be a single lead individual and at least one
backup individual for this function.
TZ mailing list: The forum where matters relating to the TZ database
and supporting code are discussed.
The rest of this document specifies the following:
1. Transferring and maintenance of the TZ mailing list;
2. Procedures for selecting a technical expert who will play the
role of TZ Coordinator and release manager for the TZ database;
3. Procedures for updating the TZ database;
4. Maintenance and ownership of reference code; and
5. Ownership of the database.
2. The TZ Mailing List
For many years, the TZ mailing list has been the forum where
discussion of changes to the TZ database and support files would take
place. In addition, the TZ mailing list is used to announce releases
of the database. Currently, the TZ mailing list is administered by
the TZ Coordinator.
This list membership, formerly at the NIH, has been transitioned to
the IANA mail server. Its address, moving forward, is <firstname.lastname@example.org>.
Subscriptions are processed at
<https://mm.icann.org/mailman/listinfo/tz/>. The TZ Coordinator will
continue to manage the list. While the TZ Coordinator may establish
other rules of governance for the list, members of that list will be
informed that a condition of participating on the list is that all
contributions to the list are released to the public domain, and that
by placing their contribution in the public domain, contributors
waive forever any intellectual property claims.
The list will be used just as it has been: to learn of, discuss, and
confirm TZ definition changes, as well as to serve as an announcement
list for new versions of the database.
3. Making Updates to the TZ Database
Updates to the TZ database are made by the TZ Coordinator in
consultation with the TZ mailing list. The TZ Coordinator is
empowered to decide, as the designated expert, appropriate changes,
but SHOULD take into account views expressed on the mailing list.
The TZ Coordinator will also decide the timing of database releases.
Today, the release itself consists of several archive files that are
downloaded from a well-known location.
Moving forward, the TZ database, supporting code, and any appropriate
supporting information SHOULD be cryptographically signed prior to
release using well known public keys, along with any appropriate
supporting information and distributed from
The criteria for updates to the database include the following:
1. New TZ names (e.g., locations) are only to be created when the
scope of the region a name was envisioned to cover is no longer
2. In order to correct historical inaccuracies, a new TZ name MAY be
added when it is necessary to indicate what was the consensus
view at a given time and location. Such TZ names are usually not
added when the inaccuracy was prior to 1970.
3. Changes to existing entries SHALL reflect the consensus on the
ground in the region covered by that entry.
To be clear, the TZ Coordinator SHALL NOT set time zone policy for a
region but use judgment and whatever available sources exist to
assess what the average person on street would think the time
actually is, or in case of historical corrections, was.
4. Selecting or Replacing a TZ Coordinator
From time to time it will be necessary to appoint a new TZ
Coordinator. This could occur for a number of reasons:
o The TZ Coordinator is retiring (as Arthur David Olson is) or has
announced that he or she will be unable to continue to perform the
o The TZ Coordinator is missing, has become incapacitated, or has
o The TZ Coordinator is not performing the function in accordance
with community wishes.
In any of these cases, members of the community should raise the
issue on the TZ mailing list and attempt to reach consensus on a new
candidate to fulfill the role of TZ Coordinator. If rough consensus
cannot be reached easily, the Area Directors of the IETF Applications
Area should attempt to guide the members of the community to rough
consensus. The candidate that is agreed upon by the community
through rough consensus shall be presented to the IESG for
confirmation. If rough consensus cannot be reached, even with
guidance from the Applications Area Directors, the IESG shall use
whatever means it has at its disposal to choose a candidate who in
its best judgment will be able to fulfill the role of TZ Coordinator.
5. Appealing Database Decisions
The TZ Coordinator makes decisions based on expertise, as well as
with guidance from the TZ mailing list. If a member of the community
has a concern with an individual decision made by the TZ Coordinator
with regard to the TZ database, the individual shall proceed as
1. Attempt to resolve the concern directly with the TZ Coordinator.
2. If a resolution cannot be reached directly with the TZ
Coordinator, express the concern to the community and attempt to
achieve rough consensus regarding a resolution on the TZ mailing
list. The Area Directors of the IETF Applications Area may at
their discretion attempt to guide the members of the community to
3. As a last resort, if a resolution cannot be reached on the TZ
mailing list, appeal to the IESG for a resolution. The appellant
must show that the decision made by the TZ Coordinator (a) was
materially in error and (b) has caused material harm. In its
deliberations regarding an appeal, the IESG shall weigh all the
evidence presented to it and use its best judgment in determining
6. Maintenance and Distribution of Reference Code
Currently, the maintainer of the TZ database also maintains reference
code, most of which is public domain. The reference implementation
shall be distributed along with an associated cryptographic signature
verifiable by a public key. Several files from this software are
currently distributed under license. Where they exist, licenses
SHALL NOT be changed.
7. Database Ownership
The TZ database itself is not an IETF Contribution or an IETF
document. Rather it is a pre-existing and regularly updated work
that is in the public domain, and is intended to remain in the public
domain. Therefore, BCPs 78 [RFC5378] and 79 [RFC3979] do not apply
to the TZ Database or contributions that individuals make to it.
Should any claims be made and substantiated against the TZ Database,
the organization that is providing the IANA Considerations defined in
this RFC, under the memorandum of understanding with the IETF,
currently ICANN, may act in accordance with all competent court
orders. No ownership claims will be made by ICANN or the IETF Trust
on the database or the code. Any person making a contribution to the
database or code waives all rights to future claims in that
contribution or in the TZ Database.
8. IANA Considerations
This section documents the following IANA actions:
o Assistance on request of the IESG in selection of the TZ
Coordinator, based on the procedures set forth above.
o Maintenance of a repository for the TZ database and associated
reference code. The TZ Coordinator SHALL be named by the IESG as
described above, and will act as the maintainer of the database
and code, as described above.
o Creation of appropriate access for the TZ Coordinator to maintain
the database, as well as necessary tooling that may be required,
so long as no direct software costs are incurred.
o Establishment of security of the system upon which the database
resides. Both current and historical versions of the database
will be stored and distributed via HTTP/HTTPS.
o Maintenance of a cryptographic private key that is used to sign
the database and that will survive a change of TZ Coordinator.
9. Security Considerations
The distribution of the database is currently not secured. This memo
states that the TZ database SHOULD be distributed with a valid
cryptographic signature moving forward.
The authors would like to thank the TZ mailing list for their
remarkable achievements over the many years. Thanks also to Marshall
Eubanks, S. Moonesamy, Peter Saint-Andre, Alexey Melenkov, Tony
Finch, Elwyn Davies, Alfred Hoenes, Ted Hardie, Barry Leiba, Russ
Housley, Pete Resnick, and Elise Gerich for the improvements they
made to this document. A special acknowledgment should be given to
Arthur David Olson for his excellent stewardship, to Rob Elz for
continuing that stewardship, and to the team at ICANN for their good
efforts, moving forward.
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of
Understanding Concerning the Technical Work of the
Internet Assigned Numbers Authority", RFC 2860,
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
[TZDB] Eggert, P. and A. Olson, "Sources for Time Zone and
Daylight Saving Time Data", 1987,
11.2. Informational References
[IEEE1003.1] Institute of Electrical and Electronics Engineers,
"Standard for Information Technology - Portable
Operating System Interface (POSIX) - Base Definitions",
IEEE Standard 1003.1-2008, December 2008.
[ISO9899C] International Standards Organization, "Information
technology -- Programming languages -- C", ISO/
IEC Standard 9899:2011, December 2011.
[RFC3979] Bradner, S., "Intellectual Property Rights in IETF
Technology", BCP 79, RFC 3979, March 2005.
[RFC4833] Lear, E. and P. Eggert, "Timezone Options for DHCP",
RFC 4833, April 2007.
[RFC5378] Bradner, S. and J. Contreras, "Rights Contributors
Provide to the IETF Trust", BCP 78, RFC 5378,
[RFC5545] Desruisseaux, B., "Internet Calendaring and Scheduling
Core Object Specification (iCalendar)", RFC 5545,
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