Du kan hantera det i din resursmodell, något som:
protected function _beforeSave(Mage_Core_Model_Abstract $object)
{
...
$date = $object->getReleaseDate();
// convert from your server/client timezone to UTC if needed
$object->setReleaseDate($this->formatDate($date));
...
}
protected function _afterLoad(Mage_Core_Model_Abstract $object)
{
...
$date = new Zend_Date($object->getReleaseDate());
// convert to your server/client timezone from UTC if needed
$object->setReleaseDate($date);
...
}