How to get first day of the week and last day of the week in sql server 2008?

Here's how you can do it:

DECLARE @yourdate date = getdate()
Select dateadd(ww, datediff(ww, 0, @yourdate), 0)
Select dateadd(ww, datediff(ww, 0, @yourdate), 4)

You set @yourdate to the date you want. The first SELECT will give you the first day and the second SELECT will give you the last date

Try this

SELECT DATEADD(wk, DATEDIFF(wk, 6, '5/13/2005'), 6)
SELECT DATEADD(wk, DATEDIFF(wk, 5, '5/13/2005'), 5)

(Or)

Declare @Date datetime
Det @Date = '2012-04-12'
Delect @Date - DATEPART(dw, @Date) + 1 FirstDateOfWeek,
       @Date + (7 - DATEPART(dw, @Date)) LastDateOfWeek

This solves it and also wraps around year ends:

SELECT DATEADD(wk, DATEDIFF(d, 0, '01 January 2017') / 7, 0)