Oxford terms are eight weeks long and the dates of term for this, and subsequent, academic years can be found on the University website.
The week preceding the first week of term is called 0th Week. Other than in the first term, you are expected to return into residence no later than 6.00 pm on the Wednesday of 0th week.
You may leave College after 7.00 pm on the Friday of 8th week if you have seen your Moral Tutor and have no further academic obligations. You must vacate your room by 10.00 am on Saturday of 8th Week.