edX courses are either self-paced or instructor-paced.
Instructor-paced courses have a fixed schedule. Course materials may be published periodically, and there may be fixed due dates. After an assignment's due date passes, you may no longer be able to complete the assignment. If you join the course late, you cannot make up any due dates you missed, but you may still be able to earn a passing score. Check your course's syllabus, calendar, or welcome module for information about the course schedule and grading policy.
Self-paced courses may feature suggested due dates. These due dates are suggestions to help you plan and pace your studies. You can submit assignments or exams any time up until the final end date of the course.
If you see a message that you have missed a suggested deadline, you can shift your due dates. This will not affect any of the progress you have made in the course so far.
Where do I see my due dates?
On a browser, you can view the end date and any due dates on the course homepage under Upcoming Dates or under the Dates tab. On the mobile app, you can check the Dates tab.