NAME

DateTime::TimeZone::Olson - timezones from the Olson database

SYNOPSIS

    use DateTime::TimeZone::Olson qw(olson_version);

    $version = olson_version;

    use DateTime::TimeZone::Olson qw(
        olson_canonical_names olson_link_names olson_all_names
        olson_links olson_country_selection);

    $names = olson_canonical_names;
    $names = olson_link_names;
    $names = olson_all_names;
    $links = olson_links;
    $countries = olson_country_selection;

    use DateTime::TimeZone::Olson qw(olson_tz);

    $tz = olson_tz("America/New_York");

DESCRIPTION

This module encapsulates the Olson timezone database, providing DateTime-compatible timezone objects and ancillary data. On each program run this module provides access to a particular version of the timezone database, determined by which version of Time::OlsonTZ::Data is installed.

FUNCTIONS

Basic information

olson_version

Returns the version number of the database to which this module is providing access. Version numbers for the Olson database currently consist of a year number and a lowercase letter, such as "2010k"; they are not guaranteed to retain this format in the future.

Zone metadata

olson_canonical_names

Returns the set of timezone names that this version of the database defines as canonical. These are the timezone names that are directly associated with a set of observance data. The return value is a reference to a hash, in which the keys are the canonical timezone names and the values are all undef.

olson_link_names

Returns the set of timezone names that this version of the database defines as links. These are the timezone names that are aliases for other names. The return value is a reference to a hash, in which the keys are the link timezone names and the values are all undef.

olson_all_names

Returns the set of timezone names that this version of the database defines. These are the "olson_canonical_names" and the "olson_link_names". The return value is a reference to a hash, in which the keys are the timezone names and the values are all undef.

olson_links

Returns details of the timezone name links in this version of the database. Each link defines one timezone name as an alias for some other timezone name. The return value is a reference to a hash, in which the keys are the aliases and each value is the canonical name of the timezone to which that alias refers. All such canonical names can be found in the "olson_canonical_names" hash.

olson_country_selection

Returns information about how timezones relate to countries, intended to aid humans in selecting a geographical timezone.

The return value is a reference to a hash, keyed by (ISO 3166 alpha-2 uppercase) country code. The value for each country is a hash containing these values:

alpha2_code

The ISO 3166 alpha-2 uppercase country code.

olson_name

An English name for the country, possibly in a modified form, optimised to help humans find the right entry in alphabetical lists. This is not necessarily identical to the country's standard short or long name. (For other forms of the name, consult a database of countries, keying by the country code.)

regions

Information about the regions of the country that use distinct timezones. This is a hash, keyed by English description of the region. The description is empty if there is only one region. The value for each region is a hash containing these values:

olson_description

Brief English description of the region, used to distinguish between the regions of a single country. Empty string if the country has only one region for timezone purposes. (This is the same string used as the key in the regions hash.)

timezone_name

Name of the Olson timezone used in this region. The named timezone is guaranteed to exist in the database, but not necessarily as a canonical name (it may be a link). Typically, where there are aliases or identical canonical zones, a name is chosen that refers to a location in the country of interest.

location_coords

Geographical coordinates of some point within the location referred to in the timezone name. This is a latitude and longitude, in ISO 6709 format.

This data structure is intended to help a human select the appropriate timezone based on political geography, specifically working from a selection of country. It is of essentially no use for any other purpose. It is not strictly guaranteed that every geographical timezone in the database is listed somewhere in this structure, so it is of limited use in providing information about an already-selected timezone. It does not include non-geographic timezones at all. It also does not claim to be a comprehensive list of countries, and does not make any claims regarding the political status of any entity listed: the "country" classification is loose, and used only for identification purposes.

Zone data

olson_tz(NAME)

Returns a reference to an object that encapsulates the timezone named NAME in the Olson database and which implements the DateTime::TimeZone interface. dies if the name does not exist in this version of the database. Currently the object is of class DateTime::TimeZone::Tzfile, but this is not guaranteed.

BUGS

Parts of the Olson timezone database are liable to be inaccurate. See "BUGS" in Time::OlsonTZ::Data for discussion. Frequent updates of the installation of Time::OlsonTZ::Data is recommended, to keep it accurate for current dates.

SEE ALSO

App::olson, DateTime::TimeZone, DateTime::TimeZone::Tzfile, Time::OlsonTZ::Data

AUTHOR

Andrew Main (Zefram) <zefram@fysh.org>

COPYRIGHT

Copyright (C) 2010, 2011, 2012, 2013, 2017 Andrew Main (Zefram) <zefram@fysh.org>

LICENSE

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.