CASE 
     WHEN (MONTH(t1.Order_Date)) IN (12, 1, 2)  THEN 1
     WHEN (MONTH(t1.Order_Date)) IN (3, 4, 5)   THEN 2
     WHEN (MONTH(t1.Order_Date)) IN (6, 7, 8)   THEN 3
     WHEN (MONTH(t1.Order_Date)) IN (9, 10, 11) THEN 4
END