For self-paced courses, you can write your exam any day on or before your course completion date pending you have provided the proper notice. The last day that you can write your exam is on your course completion date. 

For paced courses, you must write your exam during the assigned exam window.

ProctorU exams should be scheduled a minimum of 72 hours in advance and in person exams must be scheduled at least 3 weeks in advance.