We understand that there are many things that may change the timeline of your trip when traveling by car...  You may enter at any time after the start time listed on your reservation and you may depart at any time prior to the end time listed on your reservation. For example, if your reservation goes from 7AM to 7PM, you can enter and leave anytime between 7AM and 7PM.

The only thing you CANNOT do is park outside of the time you've selected.  The extra time must be purchased to avoid any penalty fees.