I once got into an argument with the clerk about that same issue, where the clerk was claiming it was a five day rental and wanted it back in four, because, they claimed, the first day was the day you rented it. So, on a two day rental, you had to return the movie the next morning by noon, even if you rented it at 11:00PM, which is only 13 hours later! It was probably people like us that they eventally changed to time to midnight on the second day instead of noon, but when they did this, they raised the rental fee by a dollar.
Did I mention I no longer go to BlockBuster and I get mad every time I drive by one?
I didn't even realize they changed the time to midnight - or raised their prices. I don't really get mad at them - I just smile when I hear things are going bad for their business.
The day of the storefront video rental business are numbered.