u can use this if it not comming
CREATE FUNCTION [dbo].[ufn_GetDaysInMonth] ( @pDate DATETIME )
RETURNS INT
AS
BEGIN
RETURN CASE WHEN MONTH(@pDate) IN (1, 3, 5, 7, 8, 10, 12) THEN 31
WHEN MONTH(@pDate) IN (4, 6, 9, 11) THEN 30
ELSE CASE WHEN (YEAR(@pDate) % 4 = 0 AND
YEAR(@pDate) % 100 != 0) OR
(YEAR(@pDate) % 400 = 0)
THEN 29
ELSE 28
END
END
END
GO