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Encyclopedia > Zoneinfo

The zoneinfo database, also called the tz database, is a collaborative compilation of information about the world's time zones, primarily intended for use with computer programs and operating systems. It is sometimes referred to as the Olson database after its prominent founding contributor Arthur David Olson. Its most recognizable feature is the uniform naming convention designed by Paul Eggert for time zones, such as “America/New_York” and “Europe/Paris”. The database also attempts to record historical time zones and all civil changes since 1970, the Unix time epoch, including transitions such as daylight saving time, and even records leap seconds. A time zone is a region of the Earth that has adopted the same standard time, usually referred to as the local time. ... 1970 (MCMLXX) was a common year starting on Thursday. ... Unix time, or POSIX time, is a system for describing points in time: it is the number of seconds elapsed since midnight UTC on the morning of January 1, 1970, not counting leap seconds. ... Though DST is common in Europe and North America, most of the worlds people do not use it. ... A leap second is a one-second adjustment to civil time in order to keep it close to the mean solar time. ...

The project's origins go back to at least 1986, and has released the database as well as some reference source code to the public domain. New editions of the database are published as changes warrant, usually several times per year. As of the 2007c edition (2007-02-26) it lists 390 primary time zones. 1986 (MCMLXXXVI) was a common year starting on Wednesday of the Gregorian calendar. ... Source code (commonly just source or code) is any series of statements written in some human-readable computer programming language. ... The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... February 26 is the 57th day of the year in the Gregorian calendar. ...


Meaning of time zone

Within the zoneinfo database, a time zone is any national or sub-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. Therefore each of the time zones defined by the zoneinfo database may document multiple offsets (relative to UTC); typically containing both the standard time and the daylight saving time in the same zone. Sometimes the number of different offsets may be larger, depending on the history of the region. Location of the Prime Meridian Prime Meridian in Greenwich The Prime Meridian, also known as the International Meridian or Greenwich Meridian, is the meridian (line of longitude) passing through the Royal Greenwich Observatory, Greenwich, England — it is the meridian at which longitude is 0 degrees. ... Coordinated Universal Time (UTC) is a high-precison atomic time standard. ... Universal Time (UT) is a timescale based on the rotation of the Earth. ... Though DST is common in Europe and North America, most of the worlds people do not use it. ...

For each time zone that has multiple offsets, usually the standard and daylight variants, the zoneinfo database records the exact moment of transition between the variants. The format can accommodate changes in the dates and times of transitions as well.

Names of time zones

The time zones in the database are given uniform names, such as “America/New_York”, in an attempt to make them easier to understand by humans and to remove ambiguity.

These names are all of the form Area/Location, where Area is the name of a continent or ocean, and Location is the name of a specific location within that region, usually cities or small islands. The set of areas currently includes: Africa, America (encompasses both North and South), Antarctica, Arctic, Asia, Atlantic, Australia, Europe, Indian, and Pacific. Additionally a special area of Etc is used for some administrative zones, particularly for “Etc/UTC” which represents Coordinated Universal Time. Animated, colour-coded map showing the various continents. ... Animated map exhibiting the worlds oceanic waters. ... Coordinated Universal Time (UTC) is a high-precison atomic time standard. ...

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 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. ISO 3166-1, as part of the ISO 3166 standard, provides codes for the names of countries and dependent areas. ...

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. 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 a few rare 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/…”.

It is important to note that the location selected is representative for the entire area, so not every city has a time zone named after it. There is for example no “America/Boston” time zone. Furthermore, different places which currently conform to the same time zone may have different names if historically they differed or are within different countries.

File formats

The zoneinfo database is published as a set of text files, which lists the rules and zone transitions in a human-readable format. For use these text files are compiled into a set of platform-independent binary files, 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 APIs such as localtime() and mktime(). It has been suggested that this article or section be merged with Plain text. ... This article is about the computing term. ... A Hexdump of a JPEG image. ... An application programming interface (API) is a source code interface that a computer system or program library provides to support requests for services to be made of it by a Length. ...

Use in software systems

The zoneinfo database is used for time zone processing and conversions in many computer software systems, including:

The Olson timezone IDs are also used by the Unicode Common Locale Data Repository (CLDR), which stores locale data in using the Locale Data Markup Language (LDML) XML standard. LDML is used for general interchange of locale data and can be used to import data into a wide variety of systems. Berkeley Software Distribution (BSD, sometimes called Berkeley Unix) is the Unix derivative distributed by the University of California, Berkeley, starting in the 1970s. ... FreeBSD is a Unix-like free operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4. ... NetBSD is a freely redistributable, open source version of the Unix-like BSD computer operating system. ... OpenBSD is a freely available Unix-like computer operating system descended from Berkeley Software Distribution (BSD), a Unix derivative developed at the University of California, Berkeley. ... DragonFly BSD is a free, Unix-like operating system which was forked from FreeBSD 4. ... Mac OS X (official IPA pronunciation: ) is a line of proprietary, graphical operating systems developed, marketed, and sold by Apple Inc. ... GNU (pronounced ) is a computer operating system composed entirely of free software. ... Unix systems filiation. ... Glibc is the GNU projects C standard library. ... DJGPP is a 32-bit C/C++/ObjC/Ada/Fortran development suite for 386+ PCs that runs under DOS (or any OS that runs DOS . ... Cygwin is a collection of free software tools originally developed by Cygnus Solutions to allow various versions of Microsoft Windows to act somewhat like a Unix system. ... The Java Runtime Environment, or JRE, is a software bundle from Sun Microsystems that allows a computer system to run a Java application. ... OpenVMS[1] (Open Virtual Memory System or just VMS) is the name of a high-end computer server operating system that runs on the VAX[2] and Alpha[3] family of computers developed by Digital Equipment Corporation of Maynard, Massachusetts (DIGITAL was then purchased by Compaq, and is now owned... An Oracle database consists of a collection of data managed by an Oracle database management system. ... Solaris is a computer operating system developed by Sun Microsystems. ... SunOS was the version of the UNIX operating system developed by Sun Microsystems for their workstations and server systems until the early 1990s. ... System V, previously known as AT&T System V, was one of the versions of the Unix computer operating system. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®) is a computer operating system originally developed in the 1960s and 1970s by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ... AIX (Advanced Interactive eXecutive) is a proprietary operating system developed by IBM based on UNIX System V. Before the product was ever marketed, the acronym AIX originally stood for Advanced IBM UNIX. The scalable AIX 5L 5. ... Tru64 UNIX is HPs (formerly Compaq; formerly DEC) 64-bit Unix operating system for the DEC Alpha AXP platform. ... UNICOS is the Unix successor of the Cray Operating System (COS) for Cray supercomputers. ... UnixWare is a flavor of the Unix operating system. ... IRIX is a computer operating system developed by Silicon Graphics, Inc. ... 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. ...

See also

A time zone is a region of the Earth that has adopted the same standard time, usually referred to as the local time. ... Though DST is common in Europe and North America, most of the worlds people do not use it. ... The zoneinfo database maintains properties of timezones, which are identified by name. ... This is a list of tz time zones as provided by the tz database. ...

External links



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