I am not the original author of these queries and have found them while surfing as usual when looking for a quick solution.
First Day Of Current Week
select CONVERT(varchar,dateadd(week,datediff(week,0,getdate()),0),106)
First Day Of Last week
select CONVERT(varchar,DATEADD(week,datediff(week,7,getdate()),0),106)
First Day Of Next Week
select CONVERT(varchar,dateadd(week,datediff(week,0,getdate()),7),106)
First Day Of Current Month
select CONVERT(varchar,dateadd(d,-(day(getdate()-1)),getdate()),106)
First Day Of Last Month
select CONVERT(varchar,dateadd(d,-(day(dateadd(m,-1,getdate()-2))),dateadd(m,-1,getdate()-1)),106)
First Day Of Next Month
select CONVERT(varchar,dateadd(d,-(day(dateadd(m,1,getdate()-1))),dateadd(m,1,getdate())),106)
First Day of Last Year
select CONVERT(varchar,dateadd(year,datediff(year,0,getdate())-1,0),106)
First Day Of Current Year
select CONVERT(varchar,dateadd(year,datediff(year,0,getdate()),0),106)
First Day Of Next Year
select CONVERT(varchar,dateadd(YEAR,DATEDIFF(year,0,getdate())+1,0),106)
Last Day Of Current Week
select CONVERT(varchar,dateadd(week,datediff(week,0,getdate()),6),106)
Last Day Of Last Week
select CONVERT(varchar,dateadd(week,datediff(week,7,getdate()),6),106)
Last Day Of Next Week
select CONVERT(varchar,dateadd(week,datediff(week,0,getdate()),13),106)
Last Day Of Current Month
select CONVERT(varchar,dateadd(d,-(day(dateadd(m,1,getdate()))),dateadd(m,1,getdate())),106)
Last Day Of Last Month
select CONVERT(varchar,dateadd(d,-(day(getdate())),getdate()),106)
Last Day Of Next Month
select CONVERT(varchar,dateadd(d,-(day(dateadd(m,2,getdate()))),DATEADD(m,2,getdate())),106)
Last Day Of Current Year
select CONVERT(varchar,dateadd(ms,-2,dateadd(year,0,dateadd(year,datediff(year,0,getdate())+1,0))),106)
Last Day Of Last Year
select CONVERT(varchar,dateadd(ms,-2,dateadd(year,0,dateadd(year,datediff(year,0,getdate()),0))),106)
Last Day Of Next Year
select CONVERT(varchar,dateadd(ms,-2,dateadd(year,0,dateadd(year,datediff(year,0,getdate())+2,0))),106)
