It’s not cast in stone that Fridays and Saturdays will be busier consistently, but it’s true most of the time. Excluding holidays Mondays are not usually extremely busy either before 5:00 pm, and probably aren’t any busier than Tuesday through Thursday for the most part. Sunday can be busy depending on whether Monday is a holiday, and numerous people have weekends off so Sunday can get busy on occasion. It can’t be 100% guaranteed that any day will be busy or not.