It can depend on the rental deal you have... For instance, weekend rates start at a certain time on a certain day. I had a National reservation for weekend rate w/ pickup at 10 am Thursday, which happened to be the time the weekend rates started. Plane came in early and I got there at 9:30 am - contract printed at double the price I had reserved because it was too early for the weekend price. So they cancelled the contract, I waited until 10 am, they printed a "correct" contract and I was on my way. Same thing may be true of weekly rates - turn a car in a day early and it may cost more. So you do need to know what you have booked.... HTH!