public function time_remaining($starttime) {
        $timeleft = $starttime + $this->properties->timelimit - time();
        $hours = floor($timeleft/3600);
        $timeleft = $timeleft - ($hours * 3600);
        $minutes = floor($timeleft/60);
        $secs = $timeleft - ($minutes * 60);

        if ($minutes < 10) {
            $minutes = "0$minutes";
        }
        if ($secs < 10) {
            $secs = "0$secs";
        }
        $output   = array();
        $output[] = $hours;
        $output[] = $minutes;
        $output[] = $secs;
        $output = implode(':', $output);
        return $output;
    }