Dallas Semiconductor has a bunch of easy to use REAL TIME CLOCK Chips.  I
recently  used the Dallas Semiconductor DS1306 in a STAMP project.  It
keeps seconds, minutes, hour, day of week, date, month and year. You read
and write to it using SPI (3 pins)- very easy to program.  The data sheet
explains how to do this.  It has on-board RAM and can be set up to trigger
an interrupt at a certain time of day. Check out their web site for info
and data sheets.  Also, the chip is relatively cheap- about $5.00.
http://www.dalsemi.com/


Foster Brashear wrote:

> I am starting work on an application which requires a PIC to sometimes
> look to a clock/calendar chip to see if it's time to do something yet.
> Of course the C/C chip has to keep running on a battery when the PIC is
> shut down, and the simpler the interface the better.  Anyone have a
> suggestion for an economical, easy-to-use C/C part?
> Thanks,  Foster