Built with the LEGO NTX platform (plus PDA support processor), the Sundial Robot uses sensor data to calculate time of day the new/old-fashioned way –
In operation, the robot rotates 360 degrees to calibrate the Compass Sensor. It then rotates in 5 degree increments, the light sensor is swept from vertical until the Touch Sensor is pushed. During the sweep the maximum light level seen is recorded. Once the robot rotates from 70 to 270 degrees magnetic, the NXT sends via bluetooth the magnetic heading where the maximum light level was seen. The PDA then calculates the time and sends the result to the NXT. The NXT then sets the clock to the time. In practice, the robot is accurate to within 15 minutes or so.
The Bulbdial Clock