Don't.
Generally speaking, it's a poor idea, because you have no idea what time zone the server is set to - and if it isn't the same as the PC your app runs on, you are going to start really annoying people... Any changes to system settings (and the time is one of those) needs to be very carefully considered, because if you do it willy-nilly, people will stop using your app and start demanding money back - I certainly would.
But if you are absolutely sure, then:
MSDN[
^] can help.