GetDate() function in sql server

select convert(varchar, DATEADD(month, DATEDIFF(month, 0, GETDATE()), 0),101) as FirstDateCurrent

select convert(varchar, DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE())+1,0)), 101) as LastDateCurrent

SELECT convert(varchar,DATEADD(mm, DATEDIFF(mm,0,getdate())+1, 0),101) as FirstDayNextMo
SELECT convert(varchar, DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE())+2,0)),101) as LastDateNext

SELECT convert(varchar,DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,GETDATE()),0)),101) as LastDatePre

SELECT convert(varchar,DATEADD(mm, DATEDIFF(mm,0,getdate())-1, 0),101) as FirstDayPrevMo


SELECT convert(varchar, DATEADD(wk,DATEDIFF(wk,0,GETDATE()),0) ,101) 'First Day of Current Week'

SELECT convert(varchar,DATEADD(wk,DATEDIFF(wk,0,GETDATE()),6),101) 'Last Day of Current Week'

SELECT convert(varchar,DATEADD(wk,DATEDIFF(wk,7,GETDATE()),0),101) 'First Day of Last Week'
SELECT convert(varchar,DATEADD(wk,DATEDIFF(wk,7,GETDATE()),6),101) 'Last Day of Last Week'

SELECT convert(varchar,DATEADD(wk,DATEDIFF(wk,-7,GETDATE()),0),101) 'First Day of Next Week'
SELECT convert(varchar,DATEADD(wk,DATEDIFF(wk,-7,GETDATE()),6),101) 'Last Day of Next Week'