The logic of Harlan's formula is trivial to prove:

If A1 has a DAY(A1)<15, then DAY(A1+6)/7 < 3, so not third Friday.

If A1 has a DAY(A1)21, then DAY(A1+6)/7 3, so not third Friday.

So only dates between the 15th and the 21st will give a TRUE result.

As for why it can't deliver 0 or 1, Harlan was only replacing the
conditional portion of your formula, which doesn't return 1 or 0. But
it's easy to extend it to do so:


=--AND(WEEKDAY(A1)=6,INT(DAY(A1+6)/7)=3)







In article ,
"arno" wrote:

but easy to understand and I explained how it works. pls. explain and
prove the logic behind your formula and tell us why it cannot deliver
0 or 1 which was requested by ramot.