How do I set the time zone in Trac?

I am struggling with setting up time zones with Trac. I have searched around but I have found nothing helpful. What can I do?

Both a whole site timezone or a per-user timezone settings would be helpful.

Solution

Default timezone for whole site is set up in the trac.ini:

[trac]
default_timezone = ...

In user preferences you have date time preferences («base_url»/prefs/datetime), where user can set his own (per user) timezone.