Thanks nbelaevski for your reply, I got it working by getting server default time zone but it raised few more questions :) , Lets say the server resides in different timezone from end user, it will be problematic then, the other option is to get the timezone settings from end user but what if the user has 'incorrect' timezone settings from the actual timezone he/she resides in?
I might be thinking too much on this.
There's no way to discover the timezone of the user by HTTP headers. That's why this forum asks for your timezone when you're registering. Just found short article on the topic via Google, you can check it out: http://mces.blogspot.com/2008/10/timezone-in-http-header.html