public function utcIsoToTimestamp($isoTime)
    {
        $utcTimeZone = new \DateTimeZone('UTC');
        $dateTime = \DateTime::createFromFormat(self::SOLR_ISO_DATETIME_FORMAT,
            $isoTime, $utcTimeZone);
        return $dateTime ? (int)$dateTime->format('U') : 0;
    }