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Let us say you need to display time for different zones or cities. Sure you can use The World Clock - Time Zones located here. If you need a different time zone at a shell prompt or script use old good date command.

Different timezones can be displayed by changing the TZ environment variable.

TZ Specifies the timezone, unless overridden by command line parameters. If neither is specified, the setting from /etc/localtime is used by Linux/UNIX computer.

Display current date and timezone

$ date
Output:

Tue Jul 24 22:05:54 CDT 2007

Display time of different timezones using the date command and TZ variable

Set timezone to PDT:
$ export TZ=America/Los_Angeles
$ date

Output:

Tue Jul 24 20:12:01 PDT 2007

Or set timezone to IST:
$ export TZ=Asia/Calcutta
$ date

Output:

Wed Jul 25 08:46:12 IST 2007

Remove the TZ variable with unset command:
$ unset TZ
$ date

Output:

Tue Jul 24 22:17:31 CDT 2007

Read date,bash,unset command man page for more information. Hope this small tip will save your time and see a different time zone.

Related: Howto: Redhat enterprise Linux / CentOS setup DST - Daylight Saving Time