Same period last month showing total month

[adam_mac]

I am using the below DAX formula to calculate prior months sales for same period as current month. For some reason however it is showing total month instead of just showing a few days of the month. I am ultimately looking to compare the net fee for 1-8 Dec against the same period in November. Attaching the raw data from excel that it should be comparing. 

PrevMTDSales = CALCULATE([TotalSales (NetValue)], DATEADD(FILTER(DATESMTD(Finance_Sales[PurchaseDate]),Finance_Sales[PurchaseDate]<TODAY()),-1,MONTH))

My "PurchaseDate" column is set as a date format so its not because of that. Any ideas why its not working?

[daxer-almighty · Accepted solution]

Time-intel functions work correctly ONLY on proper date tables, not on any tables with date columns. And what you're doing is exactly this: you're trying to use them directly on a fact table. No. This will never work.