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Operating Systems Linux How does Linux handle DST ( daylight saving time)? Post 302922091 by Corona688 on Wednesday 22nd of October 2014 11:01:51 AM
Old 10-22-2014
Not always -- it can be globally set with a file, too, /etc/localtime, which you copy from a selection in /usr/share/localtime. I copied /usr/share/zoneinfo/Canada/Saskatchewan for instance. This gives my system a timezone without having a value set for TZ.

TZ is often used to override the global setting to operate in multiple regions... and sometimes for crude date math (subtracting a number of hours), etc.
 

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DateTime::TimeZone::Local::Unix(3)			User Contributed Perl Documentation			DateTime::TimeZone::Local::Unix(3)

NAME
DateTime::TimeZone::Local::Unix - Determine the local system's time zone on Unix VERSION
version 1.63 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: o $ENV{TZ} It checks $ENV{TZ} for a valid time zone name. o /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. o /etc/timezone If this file exists, it is read and its contents are used as a time zone name. o /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. o /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. o /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. AUTHOR
Dave Rolsky <autarch@urth.org> COPYRIGHT AND LICENSE
This software is copyright (c) 2013 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. perl v5.18.2 2013-10-28 DateTime::TimeZone::Local::Unix(3)
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