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Philippe Gachoud
Asked: 2020-06-08 15:55:17 +0800 CST

Linux get UTC offset from current (or other) timezones on given date and time

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In Chile the case is very particular as the days of daylight saving changes are different a year from another...

Is there a function to get for given day at given UTC time the UTC offset?

I saw on a Suse documentation that something like zdump -v /usr/share/zoneinfo/Chile/Continental makes me enable to get all changings through years, but the job has to be done still... any command to do that?

Or/and is there a function with a given date and time from given timezone to UTC? And its reverse?

How does linux handle these changes? didn't find more documentation than Suse one.

linux timezone daylight-saving date utc

2 Answers

  1. Best Answer

    You can use the date command. You set the timezone and then specify the date and time. The command will return that time with the -03 or -04, so you will know if DST was in effect.

    For example, for Chile/Continental:

    Before DST change this year:

    $ TZ=Chile/Continental date --date='2020-04-03 11:00 +00'
Fri Apr  3 11:00:00 -03 2020

    After DST change this year:

    $ TZ=Chile/Continental date --date='2020-04-06 11:00 +00'
Mon Apr  6 11:00:00 -04 2020

    To undo that, just set TZ to UTC and change the offset:

    $ TZ=UTC date --date='2020-04-03 11:00 -04'
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  2. Based on Eduardo Trápani's answer, the final answer for me was

    • TZ=Chile/Continental date --date='TZ=Chile/Continental date --date='2020-04-05 02:00:15 +00' +%z which gives -0300
    • TZ=Chile/Continental date --date='2020-04-05 04:00:15 +00' +%z which gives -0400

    List zones

    ls -l /usr/share/zoneinfo/

    See details of a particular zone

    zdump -v /usr/share/zoneinfo/Chile/Continental

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