Last 6 months column

learner03 maybe I'm not fully understanding what you're trying to do, but it seems to me that your formula could be simplified significantly to something like :

Last 6 Months = 
VAR _CurrentDate = MAX('Calendar'[Date])
VAR _Result = 
IF(
    DATEDIFF('Calendar'[Date],_CurrentDate,MONTH) < 6,
    'Calendar'[MonthYear],
    "Neither"
)
Return
_Result

Hi learner03 

Try this:

6 months =
VAR _A =
    MAX ( 'Calendar'[Date] )
VAR _AM =
    MONTH ( _A )
VAR _6M =
    IF (
        _AM >= 6,
        DATE ( YEAR ( _A ), _AM - 5, 01 ),
        DATE ( YEAR ( _A ) - 1, 12 - ( 5 - _AM ), 01 )
    )
RETURN
    IF (
        'Calendar'[Date] >= _6M
            && 'Calendar'[Date] <= _A,
        'Calendar'[MonthYear],
        "Neither"
    )

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