public function setSkipHours(array $hours)
    {
        if (count($hours) > 24) {
            /**
             * @see Zend_Feed_Builder_Exception
             */
            require_once 'Zend/Feed/Builder/Exception.php';
            throw new Zend_Feed_Builder_Exception("you can not have more than 24 rows in the skipHours property");
        }
        foreach ($hours as $hour) {
            if ($hour < 0 || $hour > 23) {
                /**
                 * @see Zend_Feed_Builder_Exception
                 */
                require_once 'Zend/Feed/Builder/Exception.php';
                throw new Zend_Feed_Builder_Exception("$hour has te be between 0 and 23");
            }
        }
        $this->offsetSet('skipHours', $hours);
        return $this;
    }