public function setFanEveryDaySchedule($start_hour, $end_hour, $serial_number = NULL) {
        $serial_number = $this->getDefaultSerial($serial_number);
        $data = json_encode(array('fan_duty_start_time' => $start_hour*3600, 'fan_duty_end_time' => $end_hour*3600));
        return $this->doPOST("/v2/put/device." . $serial_number, $data);
    }