''' <summary>Berechnung des Buss-und Bettages</summary>
    Private Function BussUndBettag(ByVal j As Integer) As Date
        Dim christmas As Date = "25.12." & j.ToString
        BussUndBettag = DateAdd(DateInterval.Day, 0 - Weekday(christmas, _
          FirstDayOfWeek.Monday) - 4 * 7 - vbWednesday, christmas)
    End Function