LY same DAYS

shinolalady 

For this sort of calculation, I would recommend you have a separate Date table, and include Year and DayOfYearNumber columns such that corresponding weekdays from different years have the same DayOfYearNumber.

The DAX Date Template from SQLBI has such a column called FW DayOfYearNumber.

Here is an example I created:

Onedrive link

The LY Sales measure looks like this, which you can adapt to your model:

PY Sales = 
CALCULATE (
    SUM ( 'Sales'[Sales] ),
    TREATAS (
        SELECTCOLUMNS (
            'Date',
            "FW Year", [FW YearNumber] - 1,
            "FW DayOfYearNumber", [FW DayOfYearNumber]
        ),
        'Date'[FW YearNumber],
        'Date'[FW DayOfYearNumber]
    ),
    ALL ( 'Date' )
)

This measure takes the FW Year & FW DayOfYearNumber combinations from the current filter context, and shifts each year to the previous year.