DCF77 decoder with demo project
In Europe you can receive a time signal at 77.5 kHz. I connected one receiver that you can buy here at a local electronic supplier to a gadgetee socket and wrote a small modules that decodes the received time informatione.
The demo project is a clock that is synchronized every hour with the DCF77 time. The protocol is publicly available, for example here: http://en.wikipedia.org/wiki/DCF77
There are also other radio stations transmittig the encoded time: http://en.wikipedia.org/wiki/Radio_clock