The Dallas Semiconductor DS1307 Real-Time Clock is the perfect project for the Raspberry Pi, Model A. Lacking a network port, the Model A cannot determine the current date and time when it boots up. A 3 V battery attached to the DS1307 will keep its internal clock running for up to 10 years, even when the Pi is powered off. If you have a Model B, don’t feel left out. There is no reason that you can’t try this project too; a Model B not connected to a network could use the DS1307.