Current Week vs Prior Week (same year)

I've done some extensive work with weeks. What I use is the following logic:

• Get the current week number for your data. Something like this:

Prior Year Sales = 
VAR CurrentWeek =
    MAXX(
        'Sales',
        RELATED( 'Date'[Week of Year] )
    )
VAR CurrentYear =
    MAXX(
        'Sales',
        RELATED( 'Date'[Year] )
    )
VAR PriorYearSales =
    SUMX(
        FILTER(
            ALL( Sales ),
            RELATED( 'Date'[Year] ) = CurrentYear - 1
                && RELATED( 'Date'[Week of Year] ) = CurrentWeek
        ),
        Sales[SubTotal]
    )
RETURN
    PriorYearSales

You an see the 2011 week sales 23-26 are showing in the prior year for 2012 for those same weeks.

Here is a link to my PBIX file if you want to tinker with it.