Does the DateTime struct takes care of this?
Does any other class/struct?
UPDATE :
I now have read that leapseconds are only announced 6 months in advance, since the rotation of the earth is not that predictable…
Since there’s no possibility to implement that in future dates, I can imagine they just omitted them?
I think the answer to both your questions is No.
Reference: http://silverlight.net/forums/t/12114.aspx