Notify the owner as soon as possible that you are going to be late. Depending on how late you will be, the owner has the right to ask for a supplementary fee. Please be advised: Do not forget to note the time of pick up of the vehicle on the rental contract.
The owner could have a departure planned right after your return, so in order not to delay him and the next renter, please be on time.
Please know that you cannot exceed the return date, because the insurance will not cover you beyond that date. You may then be required to fully pay for repairs in the event of an accident.