Three calendar systems are used by most American colleges and universities: quarter system, semester system, and trimester system. These are ways the calendar year, measured September–August or August–August, is organized into a formal academic year. The quarter system divides the calendar year into four quarters, three of which constitute a complete academic year. Quarters are typically 10 – 12 weeks long so that three quarters amount to 30 – 36 weeks of instruction. Approximately 20% of universities are on the quarter system. 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, and an optional summer session
US Universities Typically Set Classes by Semesters. Of Course, It Is Important to Remember That Every University Will Have Its Own Specific Calendar, But Generally, The Terms Are, As Such:
The Fall Semester (Starts in August/September)
This is the first semester of the year, which starts mid-August and is less often called the autumn semester. The academic year begins this semester and most aid and assistantships are offered during this period. Moreover, most new intake is during this period.
The Spring Semester (Starts in January)
Classes begin around the first or second week of January. Most universities admit new students during this semester, but the student intake is less compared to fall. The chance of an aid is lesser but other on-campus part time jobs are available year-round, good enough to take care of your living, accommodation and personal expenses. Some universities call this the winter semester.
The Summer Semester (Around Beginning of Jun)
This is the shortest of the three semesters and spans for a period of two months and usually begins in June. Ver few universities have summer intake. Although the university, on the whole, may have summer intake, make sure the department accepts new students (this is applicable to spring as well). In several cases, regular students do not enroll for this semester and work full time on campus (40 hours per week) or take up industrial training.