Each term has 8 weeks, and the week number is often used to denote the time at which something happens.
Week 0 is also often used to denote the week before classes officially start. This is especially important in the first term of the year (Michaelmas term) where people are coming back to school and meeting old and new friends.
At the end of the year, after Trinity term, students have exams. These basically account for all of the grades. In certain courses such as the Physics course of the University of Oxford, there is only new material on Michaelmas term and Hilary term, Trinity term being revision-only. So you can imagine that during Trinity term, students are going to be on edge.
Bibliography:
Like the U.S.' fall term.
Like the U.S.' spring term.
Like the U.S.' summer term.
E-learning system prior to Canvas: weblearn.ox.ac.uk/portal. Appears fully custom and closed source?
Closed in 2023 in favour of Canvas.