Difference between two dates in weeks

CREATE FUNCTION [dbo].[WeekDiff]
(
@StartDate DateTime,
@EndDate DateTime
)
RETURNS int
AS
BEGIN
DECLARE @StartDayOfStartWeek datetime;
DECLARE @StartDayOfEndWeek datetime;

SELECT @StartDayOfStartWeek = DATEADD(d, -DATEPART(dw, @StartDate) + 1, @StartDate);
SELECT @StartDayOfEndWeek = DATEADD(d, -DATEPART(dw, @EndDate) + 1, @EndDate);
RETURN DATEDIFF(d, @StartDayOfStartWeek, @StartDayOfEndWeek)/7;
END