Make a clock using a 32768 Hz crystal and a low end PIC

32768 Hz crystals are extremely common and are used to make clocks as the number 32768 = 2^15 and can therefore be easily divided to obtain a 1 Hz pulse. Further information is provided on the Wikipedia article on quartz clocks. I believe the crystal can be used with a PIC as a secondary clock source for one of the internal timer modules which can generate an interrupt every so often with an exact frequency and therefore be used as a real time clock. Another cool blog discovered here: http://picnote.blogspot.com/ And some interesting articles:

1Hz Clock Generator using PIC12F675 Clock with 32.768KHz Crystal