DECLARE @yr INT
DECLARE @jd INT
SELECT @yr = 2002, @jd = 245
SELECT DATEADD(yyyy, @yr - 1900, -1) + @jd AS Julian_Date

Julian_Date                                            
------------------------------------------------------ 
2002-09-02 00:00:00.000

(1 row(s) affected)

Danke an Jonathan Van Houtte.