Slight Frustration With My Library

I had books that were due back to the library yesterday.  I usually like to get my books back early but just didn't have the time to make that happen this go around.  However, I did return them on time.  When I went to the library yesterday afternoon, much to my surprise, it was closed! I don't like returning my books to the outside dropbox but had no choice.  Sure enough, today I got an e-mail telling me the books were now overdue! UGH!! I'm really hoping this is just a computer glitch that will be taken care of come Tuesday.  If not, I am going to pitch a fit because I always, always, always return my books!