VB .net and Active Directory Account Expiration Date

Hi all
i am trying to add a expire date to the account with VB i found the code below and it works as long as i use two digit months ex i put 12/1/2012 and in  the attribute it says 12/1/2012 12:00:00 am,
but if i put 1/1/2012 12:00:00 am then the attribute says 12/31/2011 11:00:00 pm. any ideas what is going on?

Dim adpath As String
        Using de As New DirectoryEntry(adpath)
            Dim deUser As DirectoryEntry = New DirectoryEntry(usr)
            Dim ObjUser
           
 ObjUser = GetObject(deUser.Path)
 ObjUser.AccountExpirationDate = "1/1/2012 12:00:00 AM"
            ObjUser.SetInfo()

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