Zoneinfo
Encyclopedia
The tz database, also called the zoneinfo database or IANA Time Zone Database, is a collaborative compilation of information about the world's time zone
s, primarily intended for use with computer programs and operating systems. It is sometimes referred to as the Olson database after the founding contributor Arthur David Olson. Paul Eggert is editor and maintainer of the tz database.
Its most recognizable feature is the uniform naming convention designed by Paul Eggert for time zones, such as "America/New_York" and "Europe/Paris" (see List of tz database time zones). The database attempts to record historical time zones and all civil changes since 1970, the Unix time
epoch. It also includes transitions such as daylight saving time
, and even records leap second
s.
, is in the public domain
. New editions of the database are published as changes warrant, usually several times per year.
in the database.
As a result, on October 6, 2011, the database's maintenance (mailing list) and dissemination (FTP site) operations were shut down.
The case revolves around the use by the database maintainers of the atlases The American Atlas by Thomas G. Shanks
and The International Atlas by Thomas G. Shanks and Rique Pottenger. It specifically complains of unauthorised reproduction of the atlases' data in the timezone mailing list archive and in some auxiliary link collections maintained with the database, but doesn't actually point at the database itself. The complaint relates only to the compilation of historical timezone data, and does not cover current tzdata world timezone tables.
The tz database clearly references its sources, including the atlas, in comments, allowing the extent of use of the data to be evaluated.
took responsibility for the maintenance of the database on October 14, 2011.
The full database (including allegedly-infringing sections) and a description of current and future plans for its maintenance are available online from IANA
.
s which list the rules and zone transitions in a human-readable format. For use, these text files are compiled
into a set of platform-independent binary file
s—one per time zone. The reference source code includes such a compiler called zic (zone information compiler), as well as code to read those files and use them in standard API
s such as
This definition concerns itself first with geographic areas which have had consistent local clocks. This is different from other definitions which concern themselves with consistent offsets from a prime meridian
. Therefore each of the time zones defined by the tz database may document multiple offsets to UTC, typically containing both the standard time
and the daylight saving time
in the same zone.
and ocean
or "Etc". The set of continents and oceans currently include: Africa
, America
, Antarctica, Arctic
, Asia
, Atlantic
, Australia
, Europe
, Indian
, and Pacific
.
The special area of Etc is used for some administrative zones, particularly for "Etc/UTC" which represents Coordinated Universal Time
. In order to conform with the POSIX
style, those zone names beginning with "Etc/GMT" have their sign reversed from what most people expect. In this style, zones west of GMT have a positive sign and those east have a negative sign in their name (e.g "Etc/GMT-14" is 14 hours ahead/east of GMT.)
Country names are not used in this scheme, primarily because they would not be robust due to frequent political and boundary changes. The names of large cities tend to be more permanent. However, the database maintainers attempt to include at least one zone for every ISO 3166-1 alpha-2
country code, and a number of user interfaces to the database take advantage of this. Additionally there is a desire to keep locations geographically compact so that any future time zone changes do not split locations into different time zones.
Usually the most populous city in a region is chosen to represent the entire time zone, although other cities may be selected if they are more widely known or result in a less ambiguous name. In the event that the name of a city changes, the convention is to create an alias in future editions so that both the old and new names refer to the same database entry.
In some cases the Location is itself represented as a compound name, for example the time zone "America/Indiana/Indianapolis
". The only three-level names currently include those under "America/Argentina/...", "America/Kentucky/...", "America/Indiana/...", and "America/North_Dakota/...".
The location selected is representative for the entire area.
On 2010-05-01 Arthur David Olson mentions a 14 character limit, to justify dropping "de" as in the name of Bahia de Banderas
and using only "Bahia_Banderas" for the identifier America/Bahia Banderas
.
# This file contains a table with the following columns:
# 1. ISO 3166 2-character country code. See the file `iso3166.tab'.
# 2. Latitude and longitude of the zone's principal location
# in ISO 6709
sign-degrees-minutes-seconds format,
# either +-DDMM+-DDDMM or +-DDMMSS+-DDDMMSS,
# first latitude (+ is north), then longitude (+ is east).
# 3. Zone name used in value of TZ environment variable.
# 4. Comments; present if and only if the country has multiple rows.
#
# Columns are separated by a single tab.
# The table is sorted first by country, then an order within the country that
# (1) makes some geographical sense, and
# (2) puts the most populous zones first, where that does not contradict (1).
For example, between 1963-10-23 and 1963-12-09 in Brazil only the states of Minas Gerais
, Espirito Santo
, Rio de Janeiro
and São Paulo
had summer time, but on request a split from America/Sao Paulo
was rejected with the reasoning that since 1970 the clocks were the same in the whole region.
Time in Germany
, which is represented by Europe/Berlin
, is not correct for the year 1945 when the Trizone used different daylight saving time rules than Berlin.
, whose predecessor ISO 3166 was first published in 1974.
Proposed changes are sent to the tz mailing list, which is gatewayed to the comp.time.tz Usenet newsgroup. Source files are distributed via the FTP server elsie.nci.nih.gov. Typically, these files are taken by a software distributor like Debian
, compiled, and then the source and binaries are packaged as part of that distribution. End users can either rely on their software distribution's update procedures, which may entail some delay, or obtain the source directly from ftp://elsie.nci.nih.gov/pub/ and build the binary files themselves.
A future maintenance plan based on similar principles has been drafted through the IETF. Since 14 October IANA acts as a repository for the TZ database and associated reference code.
Pursuant to a lawsuit, the FTP server and mailing list have been shut down.
systems, including Linux distributions. The file command has support for displaying the binary timezone files in a human-friendly textual form built-in:
s to identify regions. This means all identifiers are referencing a country, something that the creators of the tz database wanted to avoid.
The Olson timezone IDs are also used by the Unicode Common Locale Data Repository
(CLDR) and International Components for Unicode
(ICU). For example, the CLDR Windows → Tzid table maps Microsoft Windows time zone IDs to the standard Olson names.
Official IANA sources
Other sources for tzdata and tzcode:
Time zone
A time zone is a region on Earth that has a uniform standard time for legal, commercial, and social purposes. In order for the same clock time to always correspond to the same portion of the day as the Earth rotates , different places on the Earth need to have different clock times...
s, primarily intended for use with computer programs and operating systems. It is sometimes referred to as the Olson database after the founding contributor Arthur David Olson. Paul Eggert is editor and maintainer of the tz database.
Its most recognizable feature is the uniform naming convention designed by Paul Eggert for time zones, such as "America/New_York" and "Europe/Paris" (see List of tz database time zones). The database attempts to record historical time zones and all civil changes since 1970, the Unix time
Unix time
Unix time, or POSIX time, is a system for describing instants in time, defined as the number of seconds elapsed since midnight Coordinated Universal Time of Thursday, January 1, 1970 , not counting leap seconds, which are declared by the International Earth Rotation and Reference Systems Service...
epoch. It also includes transitions such as daylight saving time
Daylight saving time
Daylight saving time —also summer time in several countries including in British English and European official terminology —is the practice of temporarily advancing clocks during the summertime so that afternoons have more daylight and mornings have less...
, and even records leap second
Leap second
A leap second is a positive or negative one-second adjustment to the Coordinated Universal Time time scale that keeps it close to mean solar time. UTC, which is used as the basis for official time-of-day radio broadcasts for civil time, is maintained using extremely precise atomic clocks...
s.
History
The project's origins go back to at least 1986. The project's database, as well as some reference source codeSource code
In computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...
, is in the public domain
Public domain
Works are in the public domain if the intellectual property rights have expired, if the intellectual property rights are forfeited, or if they are not covered by intellectual property rights at all...
. New editions of the database are published as changes warrant, usually several times per year.
2011 lawsuit
On September 30, 2011, a lawsuit, Astrolabe, Inc. v. Olson et al., was filed concerning copyrightCopyright
Copyright is a legal concept, enacted by most governments, giving the creator of an original work exclusive rights to it, usually for a limited time...
in the database.
As a result, on October 6, 2011, the database's maintenance (mailing list) and dissemination (FTP site) operations were shut down.
The case revolves around the use by the database maintainers of the atlases The American Atlas by Thomas G. Shanks
Thomas G. Shanks
Thomas G. Shanks is an American computer programmer, author, and time zone history researcher.-Work:While working for a San Diego based astrological computing company as programmer and research director, Shanks did extensive research in the field of worldwide timezone and daylight saving time...
and The International Atlas by Thomas G. Shanks and Rique Pottenger. It specifically complains of unauthorised reproduction of the atlases' data in the timezone mailing list archive and in some auxiliary link collections maintained with the database, but doesn't actually point at the database itself. The complaint relates only to the compilation of historical timezone data, and does not cover current tzdata world timezone tables.
The tz database clearly references its sources, including the atlas, in comments, allowing the extent of use of the data to be evaluated.
Move to ICANN
ICANNICANN
The Internet Corporation for Assigned Names and Numbers is a non-profit corporation headquartered in Marina del Rey, California, United States, that was created on September 18, 1998, and incorporated on September 30, 1998 to oversee a number of Internet-related tasks previously performed directly...
took responsibility for the maintenance of the database on October 14, 2011.
The full database (including allegedly-infringing sections) and a description of current and future plans for its maintenance are available online from IANA
Internet Assigned Numbers Authority
The Internet Assigned Numbers Authority is the entity that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System , media types, and other Internet Protocol-related symbols and numbers...
.
File formats
The tz database is published as a set of text fileText file
A text file is a kind of computer file that is structured as a sequence of lines of electronic text. A text file exists within a computer file system...
s which list the rules and zone transitions in a human-readable format. For use, these text files are compiled
Compiler
A compiler is a computer program that transforms source code written in a programming language into another computer language...
into a set of platform-independent binary file
Binary file
A binary file is a computer file which may contain any type of data, encoded in binary form for computer storage and processing purposes; for example, computer document files containing formatted text...
s—one per time zone. The reference source code includes such a compiler called zic (zone information compiler), as well as code to read those files and use them in standard API
Application programming interface
An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...
s such as
localtime and mktime.Definition of a time zone
Within the tz database, a time zone is any national region where local clocks have all agreed since 1970.This definition concerns itself first with geographic areas which have had consistent local clocks. This is different from other definitions which concern themselves with consistent offsets from a prime meridian
Prime Meridian
The Prime Meridian is the meridian at which the longitude is defined to be 0°.The Prime Meridian and its opposite the 180th meridian , which the International Date Line generally follows, form a great circle that divides the Earth into the Eastern and Western Hemispheres.An international...
. Therefore each of the time zones defined by the tz database may document multiple offsets to UTC, typically containing both the standard time
Standard time
Standard time is the result of synchronizing clocks in different geographical locations within a time zone to the same time rather than using the local meridian as in local mean time or solar time. Historically, this helped in the process of weather forecasting and train travel. The concept...
and the daylight saving time
Daylight saving time
Daylight saving time —also summer time in several countries including in British English and European official terminology —is the practice of temporarily advancing clocks during the summertime so that afternoons have more daylight and mornings have less...
in the same zone.
Names of time zones
The time zones have unique names in the form "Area/Location", e.g. "America/New_York", in an attempt to make them easier to understand by humans. A choice was also made to use English names or equivalents, and to omit punctuation and common suffixes. The underscore character is used in place of spaces. Hyphens are used where they appear in the name of a location.Area
Area is either the name of a continentContinent
A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...
and ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
or "Etc". The set of continents and oceans currently include: Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, America
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...
, Antarctica, Arctic
Arctic Ocean
The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions...
, Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, Australia
Australia (continent)
Australia is the world's smallest continent, comprising the mainland of Australia and proximate islands including Tasmania, New Guinea, the Aru Islands and Raja Ampat Islands...
, Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, Indian
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
, and Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
.
The special area of Etc is used for some administrative zones, particularly for "Etc/UTC" which represents Coordinated Universal Time
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...
. In order to conform with the POSIX
POSIX
POSIX , an acronym for "Portable Operating System Interface", is a family of standards specified by the IEEE for maintaining compatibility between operating systems...
style, those zone names beginning with "Etc/GMT" have their sign reversed from what most people expect. In this style, zones west of GMT have a positive sign and those east have a negative sign in their name (e.g "Etc/GMT-14" is 14 hours ahead/east of GMT.)
Location
Location is the name of a specific location within that region, usually cities or small islands.Country names are not used in this scheme, primarily because they would not be robust due to frequent political and boundary changes. The names of large cities tend to be more permanent. However, the database maintainers attempt to include at least one zone for every ISO 3166-1 alpha-2
ISO 3166-1 alpha-2
ISO 3166-1 alpha-2 codes are two-letter country codes defined in ISO 3166-1, part of the ISO 3166 standard published by the International Organization for Standardization , to represent countries, dependent territories, and special areas of geographical interest...
country code, and a number of user interfaces to the database take advantage of this. Additionally there is a desire to keep locations geographically compact so that any future time zone changes do not split locations into different time zones.
Usually the most populous city in a region is chosen to represent the entire time zone, although other cities may be selected if they are more widely known or result in a less ambiguous name. In the event that the name of a city changes, the convention is to create an alias in future editions so that both the old and new names refer to the same database entry.
In some cases the Location is itself represented as a compound name, for example the time zone "America/Indiana/Indianapolis
America/Indiana/Indianapolis
America/Indiana/Indianapolis is a time zone identifier in the tz database. The data is as follows: The reference point is Indianapolis, the capital and largest city of Indiana.-Covered area:The covered area is most of Indiana....
". The only three-level names currently include those under "America/Argentina/...", "America/Kentucky/...", "America/Indiana/...", and "America/North_Dakota/...".
The location selected is representative for the entire area.
On 2010-05-01 Arthur David Olson mentions a 14 character limit, to justify dropping "de" as in the name of Bahia de Banderas
Bahía de Banderas
Bahía de Banderas is both a bay and a municipality in the Mexican state of Nayarit.The bay, site of the tourist destination Puerto Vallarta, is bounded on the north by Punta Mita and on the south by Cape Corrientes...
and using only "Bahia_Banderas" for the identifier America/Bahia Banderas
America/Bahia Banderas
America/Bahia_Banderas is a time zone identifier from the zone file of the tz database. The data is as follows: The reference point is Bahia de Banderas....
.
Examples
| America/Costa Rica | name of country used because the name of the largest city San José San José, Costa Rica San José is the capital and largest city of Costa Rica. Located in the Central Valley, San José is the seat of national government, the focal point of political and economic activity, and the major transportation hub of this Central American nation.Founded in 1738 by order of Cabildo de León, San... is ambiguous |
| America/New York America/New York America/New_York is a time zone identifier in the tz database. The data is as follows: The reference point is New York City.-Covered area:The covered area with some exceptions is all of the US Eastern Time Zone.... |
Space replaced with underscore |
| Asia/Sakhalin Asia/Sakhalin Asia/Sakhalin is a time zone identifier from the zone file of the tz database. The data is as follows: The reference point is Yuzhno-Sakhalinsk-Covered area :The covered area is Sakhalin Island.... |
name of island used, because largest city, Yuzhno-Sakhalinsk Yuzhno-Sakhalinsk -Demographics:Most residents are ethnic Russians, but there also exists a sizable population of Koreans. Of the 43,000 Sakhalin Koreans, half are estimated to live in Yuzhno-Sakhalinsk, comprising roughly 12% of the city's population... , has more than 14 characters |
| America/Bahia Banderas America/Bahia Banderas America/Bahia_Banderas is a time zone identifier from the zone file of the tz database. The data is as follows: The reference point is Bahia de Banderas.... |
name of largest city altered, "de" removed from Bahia de Banderas Bahía de Banderas Bahía de Banderas is both a bay and a municipality in the Mexican state of Nayarit.The bay, site of the tourist destination Puerto Vallarta, is bounded on the north by Punta Mita and on the south by Cape Corrientes... , because correct name has more than 14 characters |
| Antarctica/DumontDUrville Antarctica/DumontDUrville Antarctica/DumontDUrville is a time zone identifier from zone file of the tz database. The data is as follows: The reference point is Dumont d'Urville Station.... |
the apostrophe is removed. Removal of space not conforming to the rule that requires replacement with "_", but with "_" the name would have 15 chars |
Data stored for each zone
For each time zone that has multiple offsets, usually the standard and daylight variants, the tz database records the exact moment of transition. The format can accommodate changes in the dates and times of transitions as well.Zone.tab
The file zone.tab is in the public domain and lists the zones. Columns and row sorting are described in the comments of the file, as follows:# This file contains a table with the following columns:
# 1. ISO 3166 2-character country code. See the file `iso3166.tab'.
# 2. Latitude and longitude of the zone's principal location
# in ISO 6709
ISO 6709
ISO 6709 Standard representation of geographic point location by coordinates is the international standard for representation of latitude, longitude and altitude for geographic point locations....
sign-degrees-minutes-seconds format,
# either +-DDMM+-DDDMM or +-DDMMSS+-DDDMMSS,
# first latitude (+ is north), then longitude (+ is east).
# 3. Zone name used in value of TZ environment variable.
# 4. Comments; present if and only if the country has multiple rows.
#
# Columns are separated by a single tab.
# The table is sorted first by country, then an order within the country that
# (1) makes some geographical sense, and
# (2) puts the most populous zones first, where that does not contradict (1).
Data before 1970
Data before 1970 aims to be correct for the city identifying the region, but is not necessarily correct for the entire region. This is because new regions are created only as required to distinguish clocks since 1970.For example, between 1963-10-23 and 1963-12-09 in Brazil only the states of Minas Gerais
Minas Gerais
Minas Gerais is one of the 26 states of Brazil, of which it is the second most populous, the third richest, and the fourth largest in area. Minas Gerais is the Brazilian state with the largest number of Presidents of Brazil, the current one, Dilma Rousseff, being one of them. The capital is the...
, Espirito Santo
Espírito Santo
Espírito Santo is one of the states of southeastern Brazil, often referred to by the abbreviation "ES". Its capital is Vitória and the largest city is Vila Velha. The name of the state means literally "holy spirit" after the Holy Ghost of Christianity...
, Rio de Janeiro
Rio de Janeiro (state)
Rio de Janeiro is one of the 27 states of Brazil.Rio de Janeiro has the second largest economy of Brazil behind only São Paulo state.The state of Rio de Janeiro is located within the Brazilian geopolitical region classified as the Southeast...
and São Paulo
São Paulo (state)
São Paulo is a state in Brazil. It is the major industrial and economic powerhouse of the Brazilian economy. Named after Saint Paul, São Paulo has the largest population, industrial complex, and economic production in the country. It is the richest state in Brazil...
had summer time, but on request a split from America/Sao Paulo
America/Sao Paulo
America/Sao_Paulo is a time zone identifier from the zone file of the tz database. The data is as follows: The reference point is São Paulo.-Covered area:...
was rejected with the reasoning that since 1970 the clocks were the same in the whole region.
Time in Germany
Time in Germany
Germany uses Central European Time and Central European Summer Time . Daylight saving time is observed from the last Sunday in March to the last Sunday in October...
, which is represented by Europe/Berlin
Europe/Berlin
Europe/Berlin is a time zone identifier from the zone file of the tz database. The data is as follows: The reference point is Berlin.-Pre-1970 differences:...
, is not correct for the year 1945 when the Trizone used different daylight saving time rules than Berlin.
Zones covering multiple post-1970 countries
There are two zones that cover an area that was covered by two countries after 1970. The tzdata follows the definitions of countries as per ISO 3166-1ISO 3166-1
ISO 3166-1 is part of the ISO 3166 standard published by the International Organization for Standardization , and defines codes for the names of countries, dependent territories, and special areas of geographical interest. The official name of the standard is Codes for the representation of names...
, whose predecessor ISO 3166 was first published in 1974.
- Asia/AdenAsia/AdenAsia/Aden is a time zone identifier from the zone file of the tz database. The data is as follows: The reference point is Aden.-Post-1970 differences:...
- two countries until 1990: North YemenNorth YemenNorth Yemen is a term currently used to designate the Yemen Arab Republic , its predecessor, the Mutawakkilite Kingdom of Yemen , and their predecessors that exercised sovereignty over the territory that is now the north-western part of the state of Yemen in southern Arabia.Neither state ever...
(Aden, People's Republic, ISO 3166-1ISO 3166-1ISO 3166-1 is part of the ISO 3166 standard published by the International Organization for Standardization , and defines codes for the names of countries, dependent territories, and special areas of geographical interest. The official name of the standard is Codes for the representation of names...
: YE) and South Yemen (Sanaa, ISO 3166-1: YD, ISO 3166-3ISO 3166-3ISO 3166-3 is part of the ISO 3166 standard published by the International Organization for Standardization , and defines codes for country names which have been deleted from ISO 3166-1 since its first publication in 1974...
YDYE). - Europe/BerlinEurope/BerlinEurope/Berlin is a time zone identifier from the zone file of the tz database. The data is as follows: The reference point is Berlin.-Pre-1970 differences:...
- two countries until 1990: East Germany (ISO 3166-1: DD, ISO 3166-3: DDDE) and West GermanyWest GermanyWest Germany is the common English, but not official, name for the Federal Republic of Germany or FRG in the period between its creation in May 1949 to German reunification on 3 October 1990....
(ISO 3166-1: DE)
Maintenance
The tz reference code and database is maintained by a group of volunteers. Arthur David Olson makes most of the changes to the code, and Paul Eggert to the database.Proposed changes are sent to the tz mailing list, which is gatewayed to the comp.time.tz Usenet newsgroup. Source files are distributed via the FTP server elsie.nci.nih.gov. Typically, these files are taken by a software distributor like Debian
Debian
Debian is a computer operating system composed of software packages released as free and open source software primarily under the GNU General Public License along with other free software licenses. Debian GNU/Linux, which includes the GNU OS tools and Linux kernel, is a popular and influential...
, compiled, and then the source and binaries are packaged as part of that distribution. End users can either rely on their software distribution's update procedures, which may entail some delay, or obtain the source directly from ftp://elsie.nci.nih.gov/pub/ and build the binary files themselves.
A future maintenance plan based on similar principles has been drafted through the IETF. Since 14 October IANA acts as a repository for the TZ database and associated reference code.
Pursuant to a lawsuit, the FTP server and mailing list have been shut down.
Unix-like systems
The standard path for the timezone database is /usr/share/zoneinfo/ on most Unix-likeUnix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
systems, including Linux distributions. The file command has support for displaying the binary timezone files in a human-friendly textual form built-in:
$ file /usr/share/zoneinfo/Europe/Berlin
/usr/share/zoneinfo/Europe/Berlin: timezone data, version 2, 8 gmt time flags, 8 std time flags, no leap seconds, 144 transition times, 8 abbreviation charsBoundaries of time zones
Geographical boundaries in form of coordinate sets are not part of the tz database, but boundaries are published by Eric Muller in the form of vector polygons. Using these vector polygons, one can determine, for each place on the globe, the tzdata zone in which it is located.Use in other standards
CLDR uses UN/LOCODEUN/LOCODE
UN/LOCODE, the United Nations Code for Trade and Transport Locations, is a geographic coding scheme developed and maintained by United Nations Economic Commission for Europe , a unit of the United Nations. UN/LOCODE assigns codes to locations used in trade and transport with functions such as...
s to identify regions. This means all identifiers are referencing a country, something that the creators of the tz database wanted to avoid.
Use in software systems
The tz database is used for time zone processing and conversions in many computer software systems, including:- BSDBerkeley Software DistributionBerkeley Software Distribution is a Unix operating system derivative developed and distributed by the Computer Systems Research Group of the University of California, Berkeley, from 1977 to 1995...
-derived systems, including FreeBSDFreeBSDFreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...
, NetBSDNetBSDNetBSD is a freely available open source version of the Berkeley Software Distribution Unix operating system. It was the second open source BSD descendant to be formally released, after 386BSD, and continues to be actively developed. The NetBSD project is primarily focused on high quality design,...
, OpenBSDOpenBSDOpenBSD is a Unix-like computer operating system descended from Berkeley Software Distribution , a Unix derivative developed at the University of California, Berkeley. It was forked from NetBSD by project leader Theo de Raadt in late 1995...
, DragonFly BSDDragonFly BSDDragonFly BSD is a free Unix-like operating system created as a fork of FreeBSD 4.8. Matthew Dillon, an Amiga developer in the late 1980s and early 1990s and a FreeBSD developer between 1994 and 2003, began work on DragonFly BSD in June 2003 and announced it on the FreeBSD mailing lists on July...
, and Mac OS XMac OS XMac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
; - the GNU C LibraryGNU C LibraryThe GNU C Library, commonly known as glibc, is the C standard library released by the GNU Project. Originally written by the Free Software Foundation for the GNU operating system, the library's development has been overseen by a committee since 2001, with Ulrich Drepper from Red Hat as the lead...
and systems that use it, including GNUGNUGNU is a Unix-like computer operating system developed by the GNU project, ultimately aiming to be a "complete Unix-compatible software system"...
, most Linux distributions, BeOSBeOSBeOS is an operating system for personal computers which began development by Be Inc. in 1991. It was first written to run on BeBox hardware. BeOS was optimized for digital media work and was written to take advantage of modern hardware facilities such as symmetric multiprocessing by utilizing...
, HaikuHaiku (operating system)Haiku is a free and open source operating system compatible with BeOS. Its development began in 2001, and the operating system became self-hosting in 2008, with the first alpha release in September 2009, the second in May 2010 and the third in June 2011....
, Nexenta OSNexenta OSNexenta OS, officially known as the Nexenta Core Platform, is a computer operating system based on OpenSolaris and Ubuntu that runs on IA-32- and x86-64-based systems. It emerged in fall 2005, after Sun Microsystems started the OpenSolaris project in June of that year. Version 1.0 was released in...
, and CygwinCygwinCygwin is a Unix-like environment and command-line interface for Microsoft Windows. Cygwin provides native integration of Windows-based applications, data, and other system resources with applications, software tools, and data of the Unix-like environment...
; - System V Release 4-derived systems, such as Solaris and UnixWareUnixWareUnixWare is a Unix operating system maintained by The SCO Group . UnixWare is typically deployed as a server rather than desktop. Binary distributions of UnixWare are available for x86 architecture computers. It was originally released by Univel, a jointly owned venture of AT&T's Unix System...
; - AIX 6.1 and later (earlier versions of AIX, starting with AIX 5.2, include zoneinfo, for support of third-party applications such as MySQLMySQLMySQL officially, but also commonly "My Sequel") is a relational database management system that runs as a server providing multi-user access to a number of databases. It is named after developer Michael Widenius' daughter, My...
, but do not use it themselves); - several other UnixUnixUnix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
systems, including Tru64, and UNICOSUnicosUNICOS is the name of a range of Unix-like operating system variants developed by Cray for its supercomputers. UNICOS is the successor of the Cray Operating System . It provides network clustering and source code compatibility layers for some other Unixes. UNICOS was originally introduced in 1985...
/mp (also IRIXIRIXIRIX is a computer operating system developed by Silicon Graphics, Inc. to run natively on their 32- and 64-bit MIPS architecture workstations and servers. It was based on UNIX System V with BSD extensions. IRIX was the first operating system to include the XFS file system.The last major version...
, still maintained but no longer shipped); - OpenVMSOpenVMSOpenVMS , previously known as VAX-11/VMS, VAX/VMS or VMS, is a computer server operating system that runs on VAX, Alpha and Itanium-based families of computers. Contrary to what its name suggests, OpenVMS is not open source software; however, the source listings are available for purchase...
; - the Java Runtime Environment since release 1.4 (2002);
- the PerlPerlPerl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...
modules DateTime::TimeZone and DateTime::LeapSecond since 2003; - PHPPHPPHP is a general-purpose server-side scripting language originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document...
releases since 5.1.0 (2005); - the PythonPython (programming language)Python is a general-purpose, high-level programming language whose design philosophy emphasizes code readability. Python claims to "[combine] remarkable power with very clear syntax", and its standard library is large and comprehensive...
module pytz; - the .NET Framework.NET FrameworkThe .NET Framework is a software framework that runs primarily on Microsoft Windows. It includes a large library and supports several programming languages which allows language interoperability...
module zoneinfo; - OracleOracle DatabaseThe Oracle Database is an object-relational database management system produced and marketed by Oracle Corporation....
releases since 10g (2004); - PostgreSQLPostgreSQLPostgreSQL, often simply Postgres, is an object-relational database management system available for many platforms including Linux, FreeBSD, Solaris, MS Windows and Mac OS X. It is released under the PostgreSQL License, which is an MIT-style license, and is thus free and open source software...
since release 8.0 (2005); - embedded software such as the firmware used in IP clocks.
The Olson timezone IDs are also used by the Unicode Common Locale Data Repository
Common Locale Data Repository
The Common Locale Data Repository Project, often abbreviated as CLDR, is a project of the Unicode Consortium to provide locale data in the XML format for use in computer applications. CLDR contains locale specific information that an operating system will typically provide to applications. CLDR is...
(CLDR) and International Components for Unicode
International Components for Unicode
International Components for Unicode is an open source project of mature C/C++ and Java libraries for Unicode support, software internationalization and software globalization. ICU is widely portable to many operating systems and environments. It gives applications the same results on all...
(ICU). For example, the CLDR Windows → Tzid table maps Microsoft Windows time zone IDs to the standard Olson names.
External links
- ITU LEGAL TIME 2011
- The tz database home page
- The tz mailing list archive
- "tz mailing list"; archives of these messages are available at ftp://elsie.nci.nih.gov/pub/tzarchive.gz.
- tz mailing list at ICANN
- “A literary appreciation of the Olson/Zoneinfo/tz database” by Jon UdellJon udellJon Udell is an "Evangelist" at Microsoft. Previously he was lead analyst for the Infoworld Test Center.Udell is author of Practical Internet Groupware, published in 1999 by O'Reilly Media, and is an advisor to O'Reilly's Safari Tech Books Online. He wrote the column "Tangled in the Threads" for...
Official IANA sources
- Home page
- [ftp://ftp.iana.org/tz FTP]
- rsync://rsync.iana.org/tz
Other sources for tzdata and tzcode:
- [ftp://elsie.nci.nih.gov/pub/ Current tz source and data raw files] - Shut down and inaccessible as of October 6, 2011 due to a civil lawsuit filed on September 30, 2011 in a federal court in Boston in which Arthur David Olson is a defendant, as per his message to the tz mailing list.
- Current tz data files compiled to multiple formats
- Lists of tz-zones by tz-group
- The tz database converted to CSV & SQL format
- Olson Database converted to Windows Standard Format
- tzcode at Apple
- tzcode at launchpad
- tzcode as part of libc in Debian
- tzdata in Debian