protected function _getRemoteMTime()
    {
        $remote_datetime = $this->_getRemoteData($this->remoteVerUrl);
        $remote_tmstp = strtotime($remote_datetime);

        if (!$remote_tmstp) {
            throw new Exception("Bad datetime format from {$this->remoteVerUrl}");
        }

        return $remote_tmstp;
    }