There is no prescribed timeline. You will graduate as soon as you complete the degree requirements. Most students finish in three regular semesters (e.g., fall, spring, fall, or spring, fall, spring) plus one summer. In the past, exceptionally well-prepared students have finished in two regular semesters; but this required a very careful planning of courses and also very hard work. Some students take four regular semesters or even longer, often because they are engaged in a significant project one way or another. Some students may take longer because they may have weak CS background and thus need to do background classes. In general, you should pace your study such that it provides the best balance between comfort and productivity.