Currently when I execute the date command from bash I get the following displayed

Thu May 17 12:21:00 IST 2012

Below is my timezone config based on executing dpkg-reconfigure tzdata

 Current default time zone: 'Europe/Dublin' Local time is now: Thu May 17 12:32:52 IST 2012. Universal Time is now: Thu May 17 11:32:52 UTC 2012. 

Any idea how I change from IST to UTC/GMT?

6 Answers

Any idea how I change from IST to GMT?

To switch to UTC, simply execute sudo dpkg-reconfigure tzdata, scroll to the bottom of the Continents list and select Etc or None of the above; in the second list, select UTC. If you prefer GMT instead of UTC, it's just above UTC in that list. :)

6

sudo timedatectl set-timezone UTC

Will change your timezone to UTC system wide.

You can do timedatectl list-timezones to see all the available timezones.

---

excerpt from @MattJohnson's answer on SO

Zones like Etc/GMT+6 are intentionally reversed for backwards compatibility with POSIX standards. See the comments in this file.

You should almost never need to use these zones. Instead you should be using a fully named time zone like America/New_York or Europe/London or whatever is appropriate for your location. Refer to the list here.

0

In the old Un*x style (SunOS, HPUX...), you can do:

ln -fs /usr/share/zoneinfo/UTC /etc/localtime

Check the contents of /usr/share/zoneinfo to get the timezone you want/need.

For instance, Irish Summer Time (IST) can be defined as

-rw-r--r-- 1 root root 3661 Mar 13 22:18 /usr/share/zoneinfo/posix/Eire

or

lrwxrwxrwx 1 root root 13 Mar 13 22:18 /usr/share/zoneinfo/Europe/Dublin -> ../posix/Eire

However, the most important is to use a proper clock reference and a ntp daemon (openntpd for instance), as timezone is only used for displaying/converting the time to strings, not to store it (whatever the timezone, difference to 01/01/1970 is everywhere the same on Earth).

1

Updated for 14.04 to present

View Time and Date Status:

$ timedatectl status Local time: Sun 2018-07-29 15:26:03 BST Universal time: Sun 2018-07-29 14:26:03 UTC RTC time: Sun 2018-07-29 14:26:03 Time zone: Europe/London (BST, +0100) System clock synchronized: yes
systemd-timesyncd.service active: yes RTC in local TZ: no

View List of Timezones:
Listed Timezones (425)

$ timedatectl list-timezones
Africa/Abidjan
Africa/Accra
Africa/Addis_Ababa
...
Pacific/Tongatapu
Pacific/Wake
Pacific/Wallis
UTC

Set Timezone to UTC:

$ timedatectl set-timezone UTC

View Time and Date Status:

$ timedatectl status Local time: Sun 2018-07-29 14:46:27 UTC Universal time: Sun 2018-07-29 14:46:27 UTC RTC time: Sun 2018-07-29 14:46:27 Time zone: UTC (UTC, +0000) System clock synchronized: yes
systemd-timesyncd.service active: yes RTC in local TZ: no*

4

Something like this?

$ date
Wed Jul 16 22:52:47 EDT 2014
$ cat /etc/timezone
America/New_York
$ sudo dpkg-reconfigure tzdata
$ service cron stop && service cron start

In case you need this for only a single command, say, ls, use this:

TZ=UTC ls -l --full-time

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