Why Must I Choose a Calendar Date for a User's New Expiration Date?

When an Admin authors a Course, you can choose a fixed Expiry Date that governs the expiration of any and all Learner Enrollments; or, a fixed number of available days that starts to count down, as soon as an individual Learner is Enrolled in your Course.

In the Edit Activity work-space however, this second option is no longer available. If you want to set a different expiration limit - it must be a calendar date, only.

The reason for this is because if you have opened a Learner's Course Activity - it is very likely that you know exactly how much time you want to give them before their Enrollment expires, therefore you can set this option quickly and easily.