How bad is it to eat expired jelly?

Haha, what a weird question. I ask because I just made myself a peanut er and jelly sandwich and then after I ate it I realized the jelly jar had August 3rd 08 as the expiration date. It didn't taste that weird, maybe a little bit tart, but not bad and I dont think anything was growing on it, I dunno, I didn't really look. Could expired jelly be really bad for you? Or will it just sort of upset your stomach a little?