Magento 1.6:Usando campos de data e hora do MySQL com modelos de recursos

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);
    ...
}