Dates and different time zones

Hello, I am creating an international site that is going to get used in both American and Europe. And I wonder how to handle the different time zones, because I want the date and time to be correct after the place your using the application. I now have the date_default_timezone_set() to "Europe/Stockholm", and all dates that is saved into the database is timestamp with time zone (using PostgreSQL). So a wonder who to handle different time zones? Have any of your experience of this? Cheers Niklas Karlsson