> talking to the PLC etc...

Not seeing the big picture what else the PIC has to do it's difficult to comment.

If it's just ensuring a Power-Up sequence to the PLC, keep rough time and maintaining a HPWM value then there's no sweat. Of course you need to ensure the equipment is on 24/7 (or otherwise provide a Battery). As soon as you put a clock-chip on a PCB, the punter starts to wonder Why? What is it for? A PIC on it's own however you can make any number of excuses why it's there.

Why is it so important to keep accurate time? If the guy pays his bill it's OK. If he doesn't, then to have it die exactly at 9pm on Wednesday 27th May 2009 (taking into account Daylight Savings time as well) is pretty irrelevant. So +/-up to 24 hours is neither here or there.

This is what gets me about the ol' Muslim Prayer times... like God is going to get the hump if you miss it by a couple of minutes!