Most Avis rentals are based on a 24-hour day.  A car rented at 10AM for a one-day rental is due back at 10AM the next day.  There is a 29-minute grace period.  If the car is returned within the 29-minute grace period there will not be any additional hourly rate. Beyond the 29-minute period, an hourly rate will apply until it equals the rate for an additional day.  Charges for optional services such as LDW, etc. are charged as full days after the 29-minute grace period.  If a vehicle is returned beyond the parameter associated with a specific rate code the rental may revert to a higher applicable rate.