Colleges typically run on a semester, quarter or modified semester system with a May or January Term. There are some small pros and cons for each, but the main difference is simply one of timing - and the vacation breaks occasionally take parents by surprise.
Semesters run about 15 weeks, so students typically leave for school in mid- to late August (and complain because their summer has been cut short and their quarter friends are still home), and return home in late May.
Semester system breaks differ markedly from the quarter calendar. Students usually get a fall break, which can range from a long weekend to an entire week off in October, as well as a two or three-day break at Thanksgiving. Unless the student has a Jan or May term, winter break typically lasts up to four weeks, with classes resuming around Jan. 20.
Summer vacation begins in mid- to late May, so students may find less competition for summer jobs when they return home. Downside? The long January break and early release in May means there may be lengthy periods when your kids are home, but their friends are not.