All I can say is "oopsie!"
We sent out invites several weeks ago, and one of the options for RSVP is to call my parents (we did online RSVP and had the phone option for the less technically-inclined). One family friend calls in his RSVP and at the end of the convo with my Mom he says "Alright, see you at 5:30 on the 16th!".
Problem is, our wedding is at 5:00.
So my Dad asks him to double check his invite. Yep. It says 5:30. What happened is I must have grabbed our mock-up invites and thrown them in with the rest when I was stuffing envelopes, meaning we've got a few incorrect invites floating around out there. Awesome! With about 200 invites sent out, it'll be SO MUCH FUN figuring out who got the wrong ones! My bad!
I'm actually pretty relaxed about it, and SO glad we did online RSVPs, because now we'll have the email address of everyone who RSVPed online (all but a few). So after the RSVP deadline, we're just going to send out a mass email saying "if your invite says 5:30, sorry - we screwed up. It's 5!"
Done and done.