Declare @StartDate date = '01-01-2018', @EndDate date = '09-30-2018'

DECLARE @PrevYearStart DATE = DATEADD(YEAR, -1, @StartDate),
    @PrevYearEnd DATE = DATEADD(YEAR, -1, @EndDate),
    @MonthStart DATE = DATEADD(MONTH,...

I think it's much simpler.  You've posted in an SSRS forum, so presumably you are doing this in SSRS.  I also presume that you are using a matrix.  In your...

Never mind.  The OP is asking for the discussion to take place here instead of where I was pointing to.

Drew

I would use a file system task instead.  No need to reinvent the wheel.

Drew

Why do you have parens around your query?

Drew

That depends on what UI you are using to display the data.  Since you didn't state, I'm assuming you mean in SSMS.  SSMS is a development environment, and is not...

I used a slightly different approach.  The problem with the previous approach is that it uses closed intervals (both end points included) when you may need to use half open intervals...