Moon light displays realtime phases

Here's a good idea - take something fun and make it functional. Hmmm, let's say a remote-controlled moon light for instance ...

I decided that it would be more interesting if the model moon actually reflected the current phase of the moon based on the date. I did this by replacing the original PCB with an arduino and a DS1307 realtime clock module from Sparkfun. The DS1307 module maintains the proper time and date, while the arduino calculates the current phase of the moon based on the date. The RTC module contains a coin cell battery backup that enables the internal clock to maintain the proper time, even without power, for up to 17 years!

From - Makezine Blog