If you need a stable time base for something such as a clock project have a look at this DIY 1Hz Time Base project from The Hackers Bench. I see that the board that was used is one from our friends at Gadget Gangster.
“In principal this circuit is extreemly simple. You build a crystal oscillator, and then you divide it’s output down to 1Hz. The crystal we’re going to use here run at 32.768 KHz ( 32768 Hz ). These are commonly called clock, or watch crystals. The significance of the value is that you can successively divide 32768 by 2 and eventually you will get to 1. There are other values that will do this (all multiples of 32768), but this value is very common. That means the crystal is cheap and easy to find.”