Can someone explain the meaning of this formula?

Excel's dates are integers that starting from a base date, which is typically 1/1/1900, but there is an option to use 1/1/1904. So, 103 years from the presumed base year of 1900 would be 2003 (unless you are using 1904 base year, you could enter =Date(103,1,1) in cell and see what it returns).