> You could also do it all inside the PIC, having it run off a
> 32kHz crystal.  Use the EEPROM or FLASH to hold the
> event times.

My thought exactly, it takes very little processor time to
check an interrupt count and compare to a table. Far less
time than communicating with another device

I have many projects involving clocks/calendars and very
very seldom use an external clock/calendar chip. The one
that does occassionally get used, which Jan-Erik mentioned,
is the PCF8593. It's I2C, so if your PIC is already busy
that won't make life any easier

What I'm saying is - if your PIC has time to deal with I2C
or other device comms, it has time for a internal timer IRQ

Mains-derived timing would be more accurate in the long-
term. You'd want a back-up battery and secondary clock
for mains outages or during relocation

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