How to calculate week differences between different data type

Hi Karnik_ ,

I suggest you to create a Calendar table to help calculation.

Calendar = 
VAR _STEP1 =
    ADDCOLUMNS (
        CALENDARAUTO (),
        "Year", YEAR ( [Date] ),
        "Month", MONTH ( [Date] ),
        "WeekStart",
            [Date] - WEEKDAY ( [Date], 2 ) + 1,
        "WeekYear",
            YEAR ( [Date] - WEEKDAY ( [Date], 2 ) + 1 )
    )
VAR _STEP2 =
    ADDCOLUMNS (
        _STEP1,
        "ActualWeek",
            RANKX (
                FILTER ( _STEP1, [WeekYear] = EARLIER ( [WeekYear] ) ),
                [WeekStart],
                ,
                ASC,
                DENSE
            )
    )
VAR _STEP3 = 
ADDCOLUMNS(_STEP2,"Workweek",RIGHT([WeekYear],2)&"W"&FORMAT([ActualWeek],"00"))
RETURN
    _STEP3

Then create a calculated column.

Difference in No.of Weeks =
VAR _START =
    CALCULATE (
        MAX ( 'Calendar'[WeekStart] ),
        FILTER ( 'Calendar', 'Calendar'[Workweek] = EARLIER ( 'Table'[Workweek] ) )
    )
VAR _END =
    CALCULATE (
        MAX ( 'Calendar'[WeekStart] ),
        FILTER ( 'Calendar', 'Calendar'[Date] = EARLIER ( 'Table'[InvCom_Date] ) )
    )
RETURN
    DATEDIFF ( _START, _END, WEEK )

Result is as below.

Best Regards,
Rico Zhou

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