public static IEnumerable<object[]> AddHours_TestData()
{
yield return new object[] { new DateTime(1986, 8, 15, 10, 20, 5, 70), 3, new DateTime(1986, 8, 15, 13, 20, 5, 70) };
yield return new object[] { new DateTime(1986, 8, 15, 10, 20, 5, 70), 0, new DateTime(1986, 8, 15, 10, 20, 5, 70) };
yield return new object[] { new DateTime(1986, 8, 15, 10, 20, 5, 70), -3, new DateTime(1986, 8, 15, 7, 20, 5, 70) };
}