protected function get_time_range_weeks_number($starttime, $endtime) {
        if ($endtime <= $starttime) {
            throw new \coding_exception('End time timestamp should be greater than start time.');
        }

        $starttimedt = new \DateTime();
        $starttimedt->setTimestamp($starttime);
        $starttimedt->setTimezone(new \DateTimeZone('UTC'));
        $endtimedt = new \DateTime();
        $endtimedt->setTimestamp($endtime);
        $endtimedt->setTimezone(new \DateTimeZone('UTC'));

        $diff = $endtimedt->getTimestamp() - $starttimedt->getTimestamp();
        return $diff / WEEKSECS;
    }