I've been wanting this same thing for years now : (
The only 'hack' i have figured out that works (but is time consuming) is to add a blank page activity into my course, and then for the past week/quarter, edit each assignment/quiz and add a Restrict Access rule to the View of that new page activity (and I keep the eyeball unslashed). Since this unslashed eyebball means students can 'see the restriction' on the course page (but actually can't since the sections these activities are in are no longer visible due to a "time restriction") this causes the activities to appear in the gradebook for the students (as un-clickable black links -- which is fine by me since they can now see the activities). I just have to remove all those restrictions for the next year.
Not ideal, but a workable hack at least...
The only 'hack' i have figured out that works (but is time consuming) is to add a blank page activity into my course, and then for the past week/quarter, edit each assignment/quiz and add a Restrict Access rule to the View of that new page activity (and I keep the eyeball unslashed). Since this unslashed eyebball means students can 'see the restriction' on the course page (but actually can't since the sections these activities are in are no longer visible due to a "time restriction") this causes the activities to appear in the gradebook for the students (as un-clickable black links -- which is fine by me since they can now see the activities). I just have to remove all those restrictions for the next year.
Not ideal, but a workable hack at least...