Update: It appears this may not work after all. And here I thought those Giz guys were crackerjacker hackers.
Renting movies from iTunes? Love it. Having to finish watching a movie within 24 hours of starting it? Not so much with the love. Fortunately, those crafty fellows over at Gizmodo figured out an easy way to turn the clock back, so to speak, thus extending your watchability window.
Basically, if you set your computer's clock ahead a few days (or weeks, or months) before starting the movie, then set it back to normal again, you'll have virtually unlimited time in which to finish watching. Already started the flick? Set the computer clock back a few days until you're able to reach the closing credits.
Apple will no doubt patch iTunes to prevent this little trick from working forever. But until then, at least you have a little more control over your rentals.