There are two due dates given to the student with each lesson: the recommended date and a final date. The recommended date is the one the student should aim for as it provides the optimal pace of learning. That is, it's soon enough after the last assignment to avoid forgetting what one has learned, and it's long enough after the last assignment that there's time to fully absorb each lesson.
But holidays and weekends sometimes make the recommended date inconvenient. For that reason we give the option of turning in assignments up to 2-3 days after the recommended due date (i.e. by the final due date).
Failure to turn in an assignment by 1 p.m. Pacific Time (4 p.m. Eastern Time), on the final due date will result in the loss of one grace period day. The system will automatically deduct the grace day and send a notification email to both the student and course sponsor when a grace day is used.
For more information about this option, read about Grace Days.