I have just been setting up a course that has three separate groups using it.
I have then set up a number of assignments, and since I do not want to clutter my course with multiples of the same assignment, I decided to use the Groups Over-ride function to set individual dates for the groups using the same assignment.
I then went to check the calendar to see if the due dates appeared there, and to my "horror" they don't, it seems that this is a bug in Moodle.
Has anyone else encountered this issue? If so, please go to the tracker for this and request that it is fixed.
This, if it is a bug, is a serious issue since students use the calendar to plan their work through a course. I really would urge anyone who makes use of the groups over-ride feature to request that this is fixed as soon as possible.