Change timezone in command line ubuntu/debian

Often we find that our time zone is not what we expect to be in our Ubuntu/Debian boxes soon after installation. Specifically in Debian these days during installation we don't have fine grained control to choose our timezone like 'Asia/Kolkatta', instead we choose 'Eastern' and later decide to change it. In order to change the timezone in command line use the following command in your Ubuntu/Debian boxes,

# dpkg-reconfigure tzdata

The above brings up an ncurses based interface where you can have fine grained control of your timezone selection.