[Koha] National holidays and other free days - how are they handled?

Hi all, How Koha handles free days, especially national holidays in the middle of a week? Is there a list where I can write down all dates when my library is closed, so the system will not allow to set return date to any day from the list, but instead set it to the first "open" day after the "closed" one? I guess I could change the return date manually, but it`s rather bad idea when there are up to 300 patrons and up to 1500 transactions per day... Any suggestions? Regards, Tomasz.