Sealed and refrigerated they aren't close to the age of some of the Grecian urns of olives pulled from the bottom of the Adriatic. Are they something you would ordinarily use (if they weren't buried in some dark corner of the fridge)? I have olives in my fridge that only get tossed when the brine seems a little off, but otherwise were used and no harm done, and I'm sure they were well-past the sell-by date.

The general answer is that olives are cheap. Probably best to toss them.