First take a look at your current time and date by running:
#date
It should display something like this:
Sat Feb 9 03:00:29 PKT 2013
To change the timezone just run the following as root and you’ll
be able to pick out your timezone from a list:
#dpkg-reconfigure tzdata
then select time zone
Synchronizing time with an NTP server
Network Time Protocol is a standard for synchronizing time across
computer networks. You can use it to synchronize your computer’s time
with exceptionally accurate time keeping devices like atomic clocks.
To synchronize time with an NTP server you have to install ntpdate:
#apt-get install ntpdate
#ntpdate us.pool.ntp.org
There are a number of NTP servers around the world. You can find a full list on ntp.org.
To make the changes stick you need to set the hardware clock on your system too:
#hwclock --systohc
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