How does Drupal display the correct time for a specific time zone?

Question

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?

Answer 1

The magic comes from PHP's date_default_timezone_set():

Sets the default timezone used by all date/time functions in a script

Drupal uses it in

• drupal_session_initialize()
• drupal_session_regenerate()
• _drupal_bootstrap_page_cache()

Answer 2

I've never seen the code itself, but it likely uses this: https://www.php.net/manual/en/datetime.settimezone.php