Compare SamePeriod Sales

Hello,

I want to compare the sales Month vs LY Month. It is fine with the non-current month, but for current month, it will only show the result upto same date last year. Is there anyway to show the last year full month sales ?

I tried below, but also cant get the result.

LY Sales = CALCULATE(SUM(Sales[SalesRetailValue]),SAMEPERIODLASTYEAR(ENDOFMONTH(DimDate[FullDate])))
LY Sales = CALCULATE(SUM(Sales[SalesRetailValue]),SAMEPERIODLASTYEAR(DimDate[FullDate]))

Would like to get help from the expert.

Thank you in advance!