If you only need compatibility back to 2005, then I guess you could call the following a "simplification".

DECLARE @pMonth INT

,@pYear INT

,@Date DATETIME

;

SELECT @pMonth = 11

,@pYear = 2013

;

SELECT FifthWeekDay = DATEADD(dd, CASE WHEN d.DoW > 1 THEN 7 ELSE 6-d.DoW END, f.FirstOfMonth-1)

FROM (SELECT DATEADD(mm,@pYear*12-22801+@pMonth,0)) f (FirstOfMonth)

CROSS APPLY (SELECT DATEDIFF(dd,-1,f.FirstOfMonth)%7) d (DoW)

;