I had a question today from a customer who was concerned that his WCF application might start to behave erratically due to the new Daylight savings schedule. Then I realized that there has been quite some noise around this area and people are predicting systems to stop responding when the new Daylight savings goes into effect. It reminded me of the Y2K days which was hyped as the doomsday of the Millennium.
In actual fact you don't have to worry about anything. WCF security has been tested for daylight savings time changes and the fact that the change happens earlier is not of concern. To be specific, WCF is using UTC time in all its code that the local time really doesn't affect us. As long as you have the Windows patch to adjust your clock at the correct time you should be fine. So, Enjoy! Keep coding with WCF!