Alright so it appears to no longer work. Here's what happened on our end. Before, we had set our computer date to 2009, and started playing Ratatouille (and Benny started playing The Simpsons) to start the 24-hour timer in 2009. Came back to 2008, everything was gravy. We go to play it again just a few minutes ago, and it tries to connect to iTunes, and then gives us a 5103 error. Benny gets the same deal.
So we delete the busted file and try a fresh download, this time with our computer dated to Jan. 24, a mere week ahead. Download starts, we click play and get the 5103 error—we couldn't even get it start in the future, which was the basis of the original trick. Adrian tried to extend a movie he rented last night by throwing his computer back a week. 5103 error, though coming back to the present he got it to play. We figured it wouldn't last forever.
It wouldn't really have mattered. iTunes 7.6.1 would have come out and smacked this loophole away.