Details
Description
Currently CiviCRM saves time in the DB according to user time & in some cases this is ahead of server time - causing delays in CiviMail.
In testing I had success using the mysql date handling to work around this - see
http://forum.civicrm.org/index.php/topic,23411.msg98329.html#msg98329
Note that I have tested in CiviMail for Drupal6. I would expect similar to work in D7 & Joomla & across the code base.
Also Tim found some timezone handling in the php code in group_contact_cache so that would need to be removed if mysql is handling timezones