Several colleges in the US use what is known as a trimester calendar for holding classes. In a trimester system, students have three semesters of approximately 10 weeks in each semester. During each of the semesters the student takes three classes.
I know what you are thinking. Only three classes? How easy would that be. But, wait. During the 10 week semester, the class covers the same amount of material that a regular two semester system covers in 15 weeks. That means that in two of the three trimesters, the students cover a full years worth of a course. Year long courses like organic chemistry take only two trimesters, not the full year like in a semester program.
There are advantages and disadvantages to a trimester calendar. One advantage is that by taking fewer courses at a time, you are able to focus more in depth on a particular subject. A second advantage is that if you don’t like the class you are taking, it will be over in less time.
The disadvantage is that because of the shortened time period for the class, everything moves at a much quicker pace. Five weeks from the start of the trimester, you have a midterm. Five weeks later you have a final. This is not a schedule for the student who wants to goof around for part of the semester and then play catch up.