Until Date and Drag and Drop was closed inappropriately
This was closed:
"It appears that when and "Until Date" is set on an assignment, and then the drag and drop feature is used in Calendar to move the assignment to a new date, the "Until Date" is not adjusted to at least the "Due Date." This causes a loss of functionality in the Drag and Drop feature of the Calendar since I still have to go in and manually adjust the "Until Date." In addition, since the "Until Date" does not show up in the short-list of dates, it cannot be fixed without multiple clicks... "
Without understanding what the issue was.
The comment was made by Joy Hall: "Calendar and the Assessment Activations are two separate tools..." There is no mention of Assessment Activations in the above paragraph. The issue is with Drag-and-Drop on the Calendar and an Until Date in an Assignment. Until Dates are used to limit the time a student has to turn-in a lab. In the Calendar an assignment can be dragged past the Until Date and the Due Date will be updated, but the Until Date will not. This results in an assignment that is Due after the last day it can be turned in (which is invalid). The result is a mess when you are importing and adjusting course dates.
Of course the Assessment Dates and the Assignment Dates for the Assessments are another confusing mess... But let's leave that for later.

Thank you for the updated feedback, Roger, however this is functioning as designed. The ‘Until’ and ‘Due’ dates are two separate features. The ‘Until’ field is used to “lock” the assignment whereas the ‘Due’ field is used for display purposes on the students end to show when the assignment is due and when it will be marked as late if submitted past that selected due date. The ‘Until’ field locks the assignments so that no submissions are available after that date, if only a ‘Due’ date with no ‘Until’ date is selected then students can still submit the assignment. Since these are two different features they do not talk to each other to update each other when one is changed by the drag and drop feature. If you have any further questions about this feature please contact the Help Desk. Thank you!
-NetAcad Support