Nah, I have did it before. Actually, I did it accidentally, because apparently I didn't get the memo that the time in the church bulletin was wrong, but alas.

I wouldn't bother mentioning it to the bride and groom, unless, it's something like, "I'm sorry I couldn't make it to the wedding, I had class," etc. Chances are they won't notice or care - they'll be happy you are there to celebrate their special day with them!