TSQL Date Manipulation

Negate Time Part (Midnight for today)

SELECT DATEADD(dd, DATEDIFF(dd,0,getdate()), 0)

Monday of the Current Week

SELECT DATEADD(wk, DATEDIFF(wk,0,getdate()), 0)

First Day of Month

SELECT DATEADD(mm, DATEDIFF(mm,0,GETDATE()), 0)

Last Day of Month

SELECT DATEADD(dd,-1,DATEADD(mm, DATEDIFF(mm,0,GETDATE())+1, 0))

First Day of the Year

SELECT DATEADD(yy, DATEDIFF(yy,0,getdate()), 0)

Last Day of Year

SELECT DATEADD(dd,-1,DATEADD(yy, DATEDIFF(yy,0,GETDATE())+1, 0))