This one is not mine but it is interesting nonetheless. This is a list of every time in $SPX history where the cash SP-500 was down at least 2% after three consecutive days of declining 7/10ths of a percent or more.
12/24/2019
08/24/2015
03/02/2009
08/31/1998
10/19/1987
05/14/1973
05/28/1962
10/21/1957
12/14/1931
05/18/1931
09/29/1930
06/09/1930
Oh, and they were all Mondays.
Oh, I forgot to add Monday 08/05/2019