whole years between dates

public static int GetDiffInWholeYears(DateTime startDate, DateTime endDate)
{
    //Excel documentation says "COMPLETE calendar years in between dates"
    int years = endDate.Year - startDate.Year;

    if (startDate.Month == endDate.Month &&// if the start month and the end month are the same
        endDate.Day < startDate.Day// AND the end day is less than the start day
        || endDate.Month < startDate.Month)// OR if the end month is less than the start month
        {
            years--;
        }

        return years;
}