public function _beforeSave()
    {
        parent::_beforeSave();

        $hlp = Mage::helper('ugiftcert');

        if ($hlp->isPattern($this->getData('cert_number'))) {
            $pattern = $this->getData('cert_number');
            $dup = Mage::getModel('ugiftcert/cert');
            $i = 0;
            while ($i++<200) { // 10 times can't find free slot - a problem
                $num = $hlp->processRandomPattern($pattern);
                $dup->load($num, 'cert_number');
                if (!$dup->getCertId()) {
                    break;
                }
                $num = false;
            }
            if ($num===false) {
                throw new Mage_Core_Exception('Exceeded maximum retries to find available random certificate number');
            }
            $this->setData('cert_number', $num);
        }

        if (Mage::getStoreConfig('ugiftcert/default/use_pin') && $hlp->isPattern($this->getData('pin'))) {
            $this->setData('pin', $hlp->processRandomPattern($this->getData('pin')));
        }

        if ($date = $this->getExpireAt()) {
            $locale = Mage::app()->getLocale();
            $format = $locale->getDateFormat(Mage_Core_Model_Locale::FORMAT_TYPE_SHORT);
            $dateObject = $locale->date($date, $format, null, false);
            $this->setExpireAt($dateObject->toString(Varien_Date::DATETIME_INTERNAL_FORMAT));
        } else {
            $this->setExpireAt(null);
        }
    }