The NYSE closed early in the weeks after the 1987 crash.
From NYSE Holiday History:
"Oct. 23-30, 1987 (Fri-Fri) Shortened hours following market break of October 19 and record breaking volume â 2:00 pm close.
Nov. 2-4, 1987 (Mon-Wed) 2:30 pm close.
Nov. 5-6, 1987 (Thu-Fri) 3:00...