ranking employees by seniority date

In what way doesn't it work? Do you get an error or the wrong results?

I am assuming it is an error because it only returns the same formula that I entered. It doesn't tell me there is an error.

If you can only see the formula in the cell then that probably means the cells are text formatted. Try changing the format of the first cell [A7?] to general then, still with that cell selected, press F2 and then ENTER. This cell should now display the correct result, copy down the column