Column header in matrix visual apply context filter only

Hi All,

I am trying to create at matrix staarting from Dec Previous Month to Dec of current Month,

I have created a DAX formulas to do so but The matrix only show me the current year,

Evolution = 

var DEC_PY = SWITCH(
                        True(),
                            Not( ISBLANK( ( SELECTEDVALUE(DimDate[Year]) ) ) ),
                            Date(SELECTEDVALUE(DimDate[Year])-1,12,31), Date(YEAR(MAX(DimDate[Year]))-1,12,31))

VAR CUR_Y = SWITCH(
                        True(),
                            Not( ISBLANK( ( SELECTEDVALUE(DimDate[Year]) ) ) ),
                            LASTDATE(DimDate[Period]),LASTDATE(DimDate[Period]))

RETURN

CALCULATE(
    SUM('Fact FTE'[Actual Work FTE]),
    filter(all(DimDate), DimDate[Date] >=
    DEC_PY ))

 
but in the Matrix I have the following display without the month of December from previous Month and the only way I can have it, it is by doing a relative date filter :

Without date filter :

With the relative filter :

If you can help me to know where is the issue,

thank you for your support