public void AddWeeks()
 {
     var date = new DateTimeOffset(2013, 7, 26, 0, 0, 0, DateTimeOffset.Now.Offset);
     Assert.AreEqual(new DateTimeOffset(2013, 8, 9, 0, 0, 0, DateTimeOffset.Now.Offset), date.AddWeeks(2));
     Assert.AreEqual(new DateTimeOffset(2013, 7, 12, 0, 0, 0, DateTimeOffset.Now.Offset), date.AddWeeks(-2));
 }