What are the differences and similarities between a quarter system and a semester system?

Both the quarter and semester models require at least 147 instructional days during the academic year. The semester system divides the year into two terms of 15 instructional weeks, typically beginning in August and ending in May. An optional summer term is also available. The quarter system divides the academic year into three terms per year of 10 weeks each, typically beginning in September and ending in June, plus an optional summer term.