nest.class.php
public function temperatureInCelsius($temperature, $serial_number = NULL) {
        $serial_number = $this->getDefaultSerial($serial_number);
        $temp_scale = $this->getDeviceTemperatureScale($serial_number);
        if ($temp_scale == 'F') {
            return ($temperature - 32) / 1.8;
        }
        return $temperature;
    }
public function temperatureInCelsius($temperature, $serial_number = NULL) {
        $serial_number = $this->getDefaultSerial($serial_number);
        $temp_scale = $this->getDeviceTemperatureScale($serial_number);
        if ($temp_scale == 'F') {
            return ($temperature - 32) / 1.8;
        }
        return $temperature;
    }
Convert a temperature value from the device-prefered scale to Celsius.

@param float  $temperature   The temperature to convert.
@param string $serial_number The thermostat serial number. Defaults to the first device of the account.

@return float Temperature in Celsius.