Hi @syada,
Another option to writing these arrayformulas to fill columns is to use brackets which create an array instead of the if row =1 formula. For example, you can do this in the top row of the column:
={"Month";arrayformula(iferror(date(year($B2:$B),month($B2:$B),1)))}
This will put “Month” in the first row and then the arrayformula starts in row 2 to the bottom. You need to use a closed } and the end of the formula.
I think this formula is a little cleaner and easier to change the Column header name.
Some earlier Tiller transactions sheets had the Date in Column A. I think that is why the example uses Column A.
Jon