All rentals are based on a 24 hour time clock. When you book your vehicle, you are putting in exact dates and times for pick up and drop off of the vehicle. The price that is generated is the offering for that exact period of time on those exact dates. If you pick up early, or return late, or change the dates for any reason, your rate will most likely change. Some companies actually charge a late return fee on top of the extra charges for the extra time you kept the vehicle. Some companies have a grace period of 25 minutes or so before they start charging a late fee, and some companies have no grace period – if you are one minute late, they start to charge you. Car companies will hold reservations for a number of hours, and some for the rest of the day for late arrivals due to airline schedules, and some will honor the rate into the next day when an airline has been delayed due to mechanical issues or bad weather. Please call us or email us if you have any questions or need help with this.