tz database

[12] The tz database is published as a set of text files which list the rules and zone transitions in a human-readable format.

A choice was also made to use English names or equivalents, and to omit punctuation and common suffixes.

The continents and oceans used are Africa, America, Antarctica, Arctic, Asia, Atlantic, Australia, Europe, Indian, and Pacific.

In order to conform with the POSIX style, those zone names beginning with "Etc/GMT" have their sign reversed from the standard ISO 8601 convention.

Country names are not normally used in this scheme, primarily because they would not be robust, owing to frequent political and boundary changes.

For each timezone that has multiple offsets (usually due to daylight saving time), the tz database records the exact moment of transition.

For example, between 1963-10-23 and 1963-12-09 in Brazil only the states of Minas Gerais, Espírito Santo, Rio de Janeiro, and São Paulo had summer time.

Arthur David Olson makes most of the changes to the tz reference code.

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 and build the binary files themselves.

The IETF has published RFC 6557, "Procedures for Maintaining the Time Zone Database" documenting best practices based on similar principles.

The standard path for the timezone database is /usr/share/zoneinfo/ in Linux distributions, macOS, and some other Unix-like systems.

The Unicode Common Locale Data Repository (CLDR) refers to zones in the tz database.

[21][22] The tz 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) and International Components for Unicode (ICU).

For example, the CLDR Windows–Tzid table maps Microsoft Windows time zone IDs to the standard Olson names, although such a mapping cannot be perfect because the number of time zones in Windows systems is significantly lower than in the IANA TZ database.

[34] On 30 September 2011, a lawsuit, Astrolabe, Inc. v. Olson et al., was filed concerning copyright in the database.