First & Last Dates of Current, Previous & Next Month

declare @DateZero datetime

declare @MonthsSinceZero int

declare @FirstofCurrentMonth datetime

declare @FirstofNextMonth datetime

declare @FirstofPreviousMonth datetime

declare @LastofCurrentMonth datetime

declare @LastofNextMonth datetime

declare @LastofPreviousMonth datetime

set @DateZero = 0

select @DateZero as DateZero

set @MonthsSinceZero = DATEDIFF(m, @DateZero, GETDATE())

-- CURRENT MONTH

set @FirstofCurrentMonth = DATEADD(mm, @MonthsSinceZero, @DateZero)

select @FirstofCurrentMonth as FirstofCurrentMonth

set @LastofCurrentMonth = DATEADD(s, -1, DATEADD(mm, @MonthsSinceZero + 1, @DateZero))

select @LastofCurrentMonth as LastofCurrentMonth

-- NEXT MONTH

set @FirstofNextMonth = DATEADD(mm, @MonthsSinceZero + 1, @DateZero)

select @FirstofNextMonth as FirstofNextMonth

set @LastofNextMonth = DATEADD(s, -1, DATEADD(mm, @MonthsSinceZero + 2, @DateZero))

select @LastofNextMonth as LastofNextMonth

-- PREVIOUS MONTH

set @FirstofPreviousMonth = DATEADD(mm, @MonthsSinceZero - 1, @DateZero)

select @FirstofPreviousMonth as FirstofPreviousMonth

set @LastofPreviousMonth = DATEADD(s, -1, DATEADD(mm, @MonthsSinceZero, @DateZero))

select @LastofPreviousMonth as LastofPreviousMonth