Calculate difference between values for same id

Hey salexa ,

I tried a little bit different approach. 

Check the following calculated column, this should give you the correct date:

Desired  output LastChanged = 
-- save the date of current row in a variable
VAR vRowDate = myTable[Date]
-- calculate first date for current Issue_ID
VAR vFirstDate =
    CALCULATE(
        MIN( myTable[Date] ),
        ALLEXCEPT(
            myTable,
            myTable[Issue_Id]
        )
    )
-- calculate the date of the last change before this row
VAR vLastChangeDate =
    CALCULATE(
        MAX( myTable[Date] ),
        ALLEXCEPT(
            myTable,
            myTable[Issue_Id]
        ),
        myTable[Desired OutPut Change] = "ChangedName",
        myTable[Date] < vRowDate
    )
RETURN
-- return the values for the different cases
    SWITCH(
        TRUE(),
        myTable[Desired OutPut Change] <> "ChangedName", BLANK(),
        vLastChangeDate = BLANK(), vFirstDate,
        vLastChangeDate
    )

And then the amount of days is an easy one:

Desired  output LastChanged Days = DATEDIFF(myTable[Desired  output LastChanged], myTable[Date], DAY)

I did some comments in the measure in order to understand better what the measure is doing.