How many days does the school year have?

A 'quarter' or 'quadmester' system divides the academic year into four quarters, each of which is usually 12 weeks long. Three of the four quarters - Fall, Winter and Spring, operating from September through June or August through May, are thus equivalent to two 18-week semesters. Thus, when American academic universities convert academic credits between the semester/trimester and quarter systems, 36 quarter hours convert to 24 semester hours (2/3 conversion factor) while 36 semester hours convert to 54 quarter hours (3/2 conversion factor).