NAME

DateTime::TimeZone::Local::Unix - Determine the local system's time zone on Unix

VERSION

version 2.21

SYNOPSIS

  my $tz = DateTime::TimeZone->new( name => 'local' );

  my $tz = DateTime::TimeZone::Local->TimeZone();

DESCRIPTION

This module provides methods for determining the local time zone on a Unix platform.

HOW THE TIME ZONE IS DETERMINED

This class tries the following methods of determining the local time zone:

  • $ENV{TZ}

    It checks $ENV{TZ} for a valid time zone name.

  • /etc/localtime

    If this file is a symlink to an Olson database time zone file (usually in /usr/share/zoneinfo) then it uses the target file's path name to determine the time zone name. For example, if the path is /usr/share/zoneinfo/America/Chicago, the time zone is "America/Chicago".

    Some systems just copy the relevant file to /etc/localtime instead of making a symlink. In this case, we look in /usr/share/zoneinfo for a file that has the same size and content as /etc/localtime to determine the local time zone.

  • /etc/timezone

    If this file exists, it is read and its contents are used as a time zone name.

  • /etc/TIMEZONE

    If this file exists, it is opened and we look for a line starting like "TZ = ...". If this is found, it should indicate a time zone name.

  • /etc/sysconfig/clock

    If this file exists, it is opened and we look for a line starting like "TIMEZONE = ..." or "ZONE = ...". If this is found, it should indicate a time zone name.

  • /etc/default/init

    If this file exists, it is opened and we look for a line starting like "TZ=...". If this is found, it should indicate a time zone name.

Note: Some systems such as virtual machine boxes may lack any of these files. You can confirm that this is case by running:

    $ ls -l /etc/localtime /etc/timezone /etc/TIMEZONE \
        /etc/sysconfig/clock /etc/default/init

If this is the case, then when checking for timezone handling you are likely to get an exception:

    $ perl -wle 'use DateTime; DateTime->now( time_zone => "local" )'
    Cannot determine local time zone

In that case, you should consult your system man pages for details on how to address that problem. In one such case reported to us, a FreeBSD virtual machine had been built without any of these files. The user was able to run the FreeBSD tzsetup utility. That installed /etc/localtime, after which the above timezone diagnostic ran silently, i.e., without throwing an exception.

SUPPORT

Bugs may be submitted at https://github.com/houseabsolute/DateTime-TimeZone/issues.

I am also usually active on IRC as 'autarch' on irc://irc.perl.org.

SOURCE

The source code repository for DateTime-TimeZone can be found at https://github.com/houseabsolute/DateTime-TimeZone.

AUTHOR

Dave Rolsky <autarch@urth.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2018 by Dave Rolsky.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

The full text of the license can be found in the LICENSE file included with this distribution.