public function getCalendarNames($calendarType = null)
    {
        $url = $this->service_url . '/jobs/calendars';
        $url .= (!empty($calendarType)) ? Util::query_suffix(array("calendarType" => $calendarType)) : null;

        $response = $this->service->prepAndSend($url, array(200), 'GET', null, true);
        if (empty($response)) return null;
        $calendars = json_decode($response);
        return $calendars->calendarName;
    }