Count unique days within month

Originally Posted by daddylonglegs

=SUM(IF(FREQUENCY(IF(MONTH(Input!B15:B2000)=8;DAY(Input!B15:B2000));ROW(INDIRECT("1:31")));1))

oops, this formula doesnt work, I think FREQUENCY is missing an argument, but im not sure how to fix it

Jirka