Vehicles can be booked overnight and for multiple consecutive days. There are two ways to do this. The most cost effective will depend on your usage needs.
Make multiple "all day" bookings. This is best if you need to use the car for the entire duration of both the first and second day. It is also the best option for bookings 3 or more days.
Make an "Overnight" booking. This is the best option when you only need the car for 24 hours.