code: 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);
      }
docs: Set the thermostat-controlled fan to run only between the specified hours.
  
  @param int    $start_hour    When the fan should start.
  @param int    $end_hour      When the fan should stop.
  @param string $serial_number The thermostat serial number. Defaults to the first device of the account.
  
  @return stdClass|bool The object returned by the API call, or FALSE on error.