You could probably find these in excel or matlab if you’re clever. For instance, if you have a column with all the dates, then something like this:
=IF(DAY(A2)=1,IF(WEEKDAY(A2,1)=7,1,0),IF(WEEKDAY(A2,1)=7,1+B1,B1))
in excel will get the number of saturdays that have passed in each month. Then you just need another column that assigns a binary value to the particular Friday before the 3rd saturday. Then just copy and paste special that into another sheet, sort on the binary and delete the ones that don’t apply, resort and you have your list of Fridays before the third Saturday in a month.