R.S.V.P. - What's that mean to me?

If you told your fans that the game would begin at 7:05, would it be fair to start the game at 6:30? How would the fans find out of the change in time?



Borrowed from Sarah Parrot's Flickr site. Photo available here. Used by permission based on Creative Commons.

Put yourself into the following situation. You receive an invitation to participate in an interesting activity. You're told that you just have to reply by a certain date. In fact, the invitation says in bold Your reply must be POSTMARKED BY AUGUST 14. But then, the invitee decides that he actually needs the reply by August 14. Is that semantics, or is that reality. How do you determine if postmarked by means "postmarked by" or "received by" ?

Sometimes it's not as simple as "RSVP."