Chris... is this for your PLC project?

If it is, you're thinking way too complex...

Example, you need the PIC to stop your PLC roughly 90 days after installation... the installation runs 24/7, so have the PIC simply keep time (with a Pause 1000) and increment EEPROM every hour. Once a day (on the 24th hour) increment EEPROM days counter. At 90 Days stop the process... you don't need great accuracy... if the PIC loses or gains a day in the process it won't matter. If the unit is switched off, too bad you could lose 59 minutes that weren't stored in EEPROM - but who cares? All you want to do is kill the equipment at some future point give or take a day or two... you could accomplish all this with a PIC16F628 running on internal Oscillator!

PS - DS1994 is obsolete!