CalculateAge.cs

        public static void CalculateAge(DateTime dt1, DateTime dt2, out int years, out int months, out int days)
        {
            DateTime start = dt1 < dt2 ? dt1 : dt2;
            DateTime end = dt2 > dt1 ? dt2 : dt1;

            years = 0;
            months = 0;
            days = 0;

            while (start.AddYears(1) < end)
            {
                start = start.AddYears(1);
                years++;
            }

            while (start.AddMonths(1) < end)
            {
                start = start.AddMonths(1);
                months++;
            }

            while (start.AddDays(1) < end)
            {
                start = start.AddDays(1);
                days++;
            }
        }