Custom invoice period (25th - 25th) - can't make up the formula

Hi there.

I have a customer with custom invoice period - 25th of prev month till 25th on current month.

What i need is to see hours spent in this period monthly, but pBI data hierarchy works with standard month period only.

So far i tried to make custom column in my data table with smth like this:

Column = IF('Date'[DayOfMonthNumber]<25;PREVIOUSMONTH('Date'[MM/DD/YYYY]);NEXTMONTH('Date'[MM/DD/YYYY]))

But it doesnt work for me

Thanks in advance!