How does Drupal display the correct time for a specific time zone? I have a custom module that displays today's date and time:

t('Today: ') . date('d F - H:i')


When I change a user's time zone on their account page the time is 'magically' outputted correctly.

How does Drupal do this?
I've never seen the code itself,  but it likely uses this: http://ca3.php.net/manual/en/datetime.settimezone.php