Unopened, a jar of pasta sauce is good basically indefinitely, but as soon as you actually open the jar the clock starts ticking. We don't make enough pasta at a time to use a full jar, (and in fact will usually use a small fraction of the jar) so I write the date that I opened the jar on the lid to plan its use a little better. "Hey, better find a use for this sauce, it's going to go bad eventually."