Time is relative. Einstein knew it, Jack Bauer knows it and now Apple has proved it by extending the 24 hours watching window for iTunes movie rentals.

US iTunes Movie Rental Store users have discovered that movies continue to play even after they've expired - you're presented with a dialogue box that asks you to Resume or Delete the movie in question.

The trick is to pause the movie and then go off and do something else for a while - like go to sleep, go shopping or deal with a family emergency. The iTunes Movie Rentals Store gives you the option to carry on watching on the screen you last used - a rare example of practicality and good PR in this money-grabbing age.

You could argue, of course, that Apple had to do something like this - it desperately needs the Apple TV and the iTunes Movie Rental Store to be a success and so has to wheel punters in. Apple also has to compete with DVD movie rental services that don't punish you with either late fees or mysteriously disappearing products.

We hope that Apple remembers to include this functionality should iTunes Movie Rentals eventually surface over here.