Every month, the dates of four Wednesdays are 7 in turn.

The last three Wednesdays are 7 14 2 1 larger than the first one.

Then 66-7- 14-2 1 is four times the date of the first Wednesday.

Then the first Wednesday is (66-7- 14-2 1)/4=6.

Then the number one is 3+7-(6- 1)=5, Friday.