Yes, the entire calendar. Try memorizing your department's sections. Nothing will help you more. There are plenty of things which have to be taken care of, and the only way someone can know them is to read everything one can get one's hands on. Calendar information isn't enough.
Deadlines change all the time, and course requirements also change.
Coming from someone who has been there, do your own research. Find out from publications what you are supposed to do. Don't go to someone and try to get them to tell you what you need or have to do unless you have searched for the answer and can't find it. During registration time, the sheer volume of students who rush around like chickens with their heads cut off make it difficult for regular students to get any help at all. Well, more often than not, the answers are in the calendar.