Get Start and End date of Fortnight

Sometime it is needed to get the start and end date of fortnight.
Use below query to get the result:


DECLARE @DateInput DATETIME
SET @DateInput = '28-Jan-2013'

DECLARE @FNStartDate DATETIME
DECLARE @FNEndDate DATETIME

IF DAY(@DateInput) < 16  -- First Half of Month
BEGIN
SET @FNStartDate = CAST(CAST(YEAR(@DateInput) AS VARCHAR(4)) + '/' + CAST(MONTH(@DateInput) AS VARCHAR(2)) + '/01' AS DATETIME)
SET @FNEndDate = CAST(CAST(YEAR(@DateInput) AS VARCHAR(4)) + '/' + CAST(MONTH(@DateInput) AS VARCHAR(2)) + '/15' AS DATETIME)
END
ELSE -- Second Half of Month
BEGIN
SET @FNStartDate = CAST(CAST(YEAR(@DateInput) AS VARCHAR(4)) + '/' + CAST(MONTH(@DateInput) AS VARCHAR(2)) + '/16' AS DATETIME)
SET @FNEndDate = DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,@DateInput)+1,0))
END

SELECT @FNStartDate AS 'StartDate', @FNEndDate AS 'EndDate'