public void ValidatedBissextYear() { //Output 29/02/2016 17:00 datetime = DateTime.Parse("28/02/2016 17:00"); string microsoft_result = datetime.AddHours(24).ToString("dd/MM/yyyy HH:mm"); string new_datetime = my_datetime.AddHours("28/02/2016 17:00", 24); string my_result = my_datetime.Format(new_datetime, 1); Assert.AreEqual(microsoft_result, my_result); }