When do most schools require that applications be submitted?

Most schools have application deadlines, and these can vary depending on the school and program. Some schools have early action or early decision deadlines, which are earlier than regular deadlines. For undergraduate admissions, common application deadlines are in January or February for regular decision, and in November or December for early action or early decision. For graduate admissions, deadlines can vary widely depending on the program, but many have deadlines in December, January or February. It's important to check with the specific schools you are interested in for their application deadlines and requirements.