MichaelMeissner:
BTW, an alternative to the RTC if you have the Arduino on your network (either with an ethernet shield or wifi) is to use the Network Time Protocol: http://arduino.cc/en/Tutorial/UdpNtpClient.
Another alternative (if you live in Europe or North Americas) is a time signal receiver, for example http://www.pvelectronics.co.uk/index.php?main_page=product_info&products_id=2.