Market Closed Calendar - MLK day 1986-1997


I while back I found the Market Holidays link, and it's really handy. I've created an Excel Power Query function that returns the Market Holidays for any year requested based on that link plus year.
However, that calendar lists MLK day as a Market Holiday starting in 1986, but when using Excel's STOCKHISTORY function, the days reported between 1986 and 1997 show the market as being open, and downloading historical price data from Yahoo confirms this.
Is there a reason MLK day is listed as a Market Holiday for those years (1986-1997)? I realize it was first observed in 1996, but that appears to be different from when the market was closed.
Thank you.

That was most probably a mistake on our (MyPivots) part as not knowing at that time that MLK wasn't observed as a market holiday until 1998.
@jdellasala - this is fixed now.