Problem with SAMEPERIODLASTYEAR

Hi,

I have a wierd issue with SAMEPERIODLASTYEAR function. I am calculating the running total percentage over the actual revenue for each quarter. Let's call this Attainment.

Now, I am trying to compare the attainment values between two years.

I have data for all the dates for the fiscal quarters from previous years (From Jan 1 - Mar 31). And for the current quarter, I have only the data upto the current date. (From Jan 1 - Feb 26). Now when I try to lookup the Attainment value from prev year for the same date using the below formula,

AttainmentLY = CALCULATE([Attainment], SAMEPERIODLASTYEAR(DimDate[Date]))

I get same values for Attainment and AttainmentLY. How is this possible?

There is a one-many relationship between the date columns of DimDate and Sales tables.