Yes, you may block guests from booking a reservation that arrives or departs on specific days of the year. For example, if you do not want guests to be able to check in or check out on Christmas Day, you can restrict that day. BrightSide allows you to restrict a check-in, check-out, or both, on any day of the year.
This setting does not prevent a reservation from including a restricted day in the stay. It only prevents them from checking in or out on that day.