I didn't think they still date stamped in the mid-80's either. I had never seen anything date stamped after 1980, or with a written arrival date after 1982.
Until today, that is:
Latest date stamp on these books is January 28, 1986!
Which is the day the Space Shuttle Challenger exploded.
Anyway, no sign of a September 16 date among them, but apparently it's at least theoretically possible.
There's hope for even later date stamps. Unfortunately, this one doesn't hit a want list date. I love the date placement and Sleepwalker #1 is