Apply before your program's deadline! Some programs and departments have deadline dates as early as December or January (for the next fall term), so it is extremely important to know the application deadline for your program of interest. Applicants who submit after deadlines might NOT be considered for admission. To avoid delays due to unforeseen circumstances, it is strongly recommended that you complete your application at least two weeks before the deadline. Also keep in mind that some programs consider applications for the fall term only.
Some graduate and professional programs may have rolling admission, which means they accept applications on an ongoing basis year round. If this is the case with your program of interest, you should still apply as early as possible, and no later than one month before the next term begins. Fall term begins in late August, Spring term in mid-January, and Summer term in early June.