public void PreviousYear_IfPreviousYearDoesNotHaveTheSameDayInTheSameMonthThenCalculateHowManyDaysIsMissingAndAddThatToTheLastDayInTheSameMonthPreviousYear()
 {
     var someBirthday = new DateTimeOffset(2012, 2, 29, 17, 0, 0, 0, TimeSpan.Zero);
     var previousYear = someBirthday.PreviousYear();
     Assert.AreEqual(new DateTimeOffset(2011, 3, 1, 17, 0, 0, 0, TimeSpan.Zero), previousYear);
 }
 public void PreviousYear_ReturnsTheSameDateButPreviousYear()
 {
     var birthday = new DateTimeOffset(1976, 12, 31, 17, 0, 0, 0, TimeSpan.Zero);
     var previousYear = birthday.PreviousYear();
     Assert.AreEqual(new DateTimeOffset(1975, 12, 31, 17, 0, 0, 0, TimeSpan.Zero), previousYear);
 }