Once a rental request has been sent, it is not possible to adjust it. This has to do with the insurance that has already been established for the booked period. The check-in of the booking is available 30 minutes before the start of the rental. If you want to start the booking earlier, we advise you to cancel the booking and make a new booking with the correct dates and times.
An extension can be requested but extra costs may apply. Read more about that here.