Semesters are traditionally tied to seasons of the year. At the university level:
- The fall semester runs roughly from late August to mid December.
- The spring semester runs roughly from late January to early May.
- The summer semester runs roughly from early June to mid August and may be divided into two or more distinct (but sometimes overlapping) sessions.
Some schools prefer to use the quarter system instead.
Over the course of a semester, a typical university class will usually include approximately 39–43 hours of classroom instruction, but may include more or less depending on the university, the semester, the class and the number of credit hours associated with the class.