The traditional start date for the school year has been the Tuesday following the first Monday in September (the day after Labor Day). Though some schools still keep this tradition, many schools now start in the last two weeks of August and some schools in the first week in October. There are also some schools that begin at the end of July and early August. Most colleges that use the quarter system have: • a fall quarter from late September to mid-December; • a winter quarter from early January to mid-March; • a spring quarter from late March or early April to mid-June; • an optional summer session. Most universities on the semester system have: • a fall semester from the day after Labor Day in September to mid-December; • a spring/winter semester from late January to early May; • an optional summer session. College grades, determined by each instructor on the basis of class work and examinations, are usually on a five point scale, with letters to indicate the levels of achievement.