When I was in Prague in May, I had booked all of our wedding guests into the Renaissance. One of my friends had given me the wrong date for his flight home, meaning he had an extra night booked that he didn't really need. His flight was around 9pm so he kept the room for that day and then went to check out at around 7pm. The desk clerk said 'but you're supposed to be staying tonight as well' and he explained what had happened. The clerk only charged him a nominal amount for that last day as he had checked out early.

I would either call the hotel before or have a word with the front desk when you get there. I'm sure it would not be a problem.