Calculate Percentage Change With a Relative Date Slicer

Hi AnF0 

Create a numeric range parameter table. Assuming the name of the table created is LastXDays, the name of the automatically crate measure is also the same, create these measures. 

Last X Days = 
VAR _MaxDate =
    CALCULATE ( MAX ( Dates[Date] ), ALLSELECTED ( Dates ) )
VAR _StartDate = _MaxDate - [LastXDays Value] + 1
RETURN
    CALCULATE (
        [Total Revenue],
        KEEPFILTERS ( Dates[Date] >= _StartDate && Dates[Date] <= _MaxDate )
    )

Last X Days Prior = 
VAR _MaxDate =
    CALCULATE ( MAX ( Dates[Date] ), ALLSELECTED ( Dates ) )
VAR _EndDate = _MaxDate - [LastXDays Value] - 1
VAR _StartDate = _EndDate - [LastXDays Value] + 1
RETURN
    CALCULATE (
        [Total Revenue],
        KEEPFILTERS ( Dates[Date] >= _StartDate && Dates[Date] <= _EndDate )
    )

Last X Days Variance = 
[Last X Days] - [Last X Days Prior]

Last X Days Delta = 
DIVIDE ( [Last X Days Variance], [Last X Days Prior] )

Note: In the above example, the _MaxDate  is is the max of all the visible Dates[Date] rows. Please see the attached sample pbix.