Charging For Extra Days While Closed

Can Hertz charge me for extra days after I return the car due to the fact that they are closed.  I rented a car for two days, but when I returned it they were closed.  Upon dropping the keys in the drop box, I read a sign indicating that I will be charged for my rental until the facility reopens.  Well this location was closed for thee consecutive days.  That's five days of rental when I only had the car for 2 days.