There are a series of time zone files located at
/usr/share/zoneinfo and active timezone used on your system is in the /etc/localtime file. You can change the current time to Paksitan Standard Time (PKT/GMT+5) by follwoing commands.$ date
Thu 4 Feb 05:54:51 UTC 2016
$ mv /etc/localtime /etc/localtime.bkp
$ ln -s /usr/share/zoneinfo/Asia/Karachi /etc/localtime
$ date
Thu 4 Feb 10:55:12 PKT 2016
$
you can also configure other timezone by locating in following directory
/usr/share/zoneinfo/Etc/GMT+5