How to Dynamically Subtract Variable Days?

[TimmK]

For simplicity I have a table with the three columns "Order Key", "Date" and "Days".

I would like to use a DAX measure (or if this is not possible a calculated column) to subtract the days from the date for each row. Additionally, if the result of the calculation is a date that is on a Saturday another day should be subtracted and if it is a Sunday two additional days should be subtracted. How can I do this?

[FreemanZ]

Try this:

 

Adjusted date =

VAR ReferenceDate =

    SELECTEDVALUE ( 'Table'[Date] )

VAR ReferenceDays =

    SELECTEDVALUE ( 'Table'[Days] )

VAR BaseDate = ReferenceDate - ReferenceDays

VAR Result =

    SWITCH ( 

    WEEKDAY ( BaseDate ), 

    1, BaseDate - 4,

    2, BaseDate - 5,

    3, BaseDate - 5,

    4, BaseDate - 5,

    BaseDate - 3

)

RETURN

    Result

[TimmK]

Thanks, but this results in a lot of additional rows and wrong dates. 😕

[johnt75 · Accepted solution]

You could create a measure like

Adjusted date =
VAR ReferenceDate =
    SELECTEDVALUE ( 'Table'[Date] )
VAR ReferenceDays =
    SELECTEDVALUE ( 'Table'[Days] )
VAR BaseDate = ReferenceDate - ReferenceDays
VAR Result =
    SWITCH ( WEEKDAY ( BaseDate ), 1, BaseDate - 2, 7, BaseDate - 1, BaseDate )
RETURN
    Result

[TimmK]

@johnt75 Ah, actually the last part unfortunately does not work as intended. For example, let us say the reference date is November 21, 2022 (Monday) and 3 days should be subtracted. Then based on your measure the result would be November 18, 2022 (Friday). However, it actually should be November 16, 2022 (Wednesday) because it should be 3 workdays earlier, which means November 21, 2022 - 2 weekend days - 3 workdays.

Could you please help with a solution?

[johnt75]

Try

Adjusted date =
VAR ReferenceDate =
    SELECTEDVALUE ( 'Table'[Date] )
VAR ReferenceDays =
    SELECTEDVALUE ( 'Table'[Days] )
VAR BaseDate = ReferenceDate - ReferenceDays
VAR WorkingDaysDiff =
    NETWORKDAYS ( BaseDate, ReferenceDate )
VAR Result = BaseDate - ( ReferenceDays - WorkingDaysDiff )
RETURN
    Result

[TimmK]

This is what I get with the updated measure:

Almost there. If the date is 2022-11-16 (WED) and 2 days should be subtracted then the result should be 2022-11-14 (MON) instead of 2022-11-15 (TUE). It seems that addtional 1 day needs to be subtracted for each row.

Also, for example if the date is 2022-11-16 (WED) and 3 days should be subtracted then the result should be 2022-11-11 (FRI) instead of 2022-11-13 (SUN).

Additional question: How can I remove the 30.12.1899 from the total?

Thank you very much for your great help.

[johnt75]

I think maybe a different approach. Add a column to your date table, Is Working Day, which returns 1 if the day is not a weekend. Then you can create a measure like

Adjusted date =
IF (
    ISINSCOPE ( 'Table'[Date] ),
    VAR ReferenceDate =
        SELECTEDVALUE ( 'Table'[Date] )
    VAR ReferenceDays =
        SELECTEDVALUE ( 'Table'[Days] )
    VAR WorkingDates =
        CALCULATETABLE (
            TOPN ( ReferenceDays, 'Date', 'Date'[Date], DESC ),
            'Date'[Date] < ReferenceDate,
            'Date'[Is Working Day] = 1
        )
    RETURN
        MINX ( WorkingDates, 'Date'[Date] )
)

[TimmK]

This seems to have the correct result. Yet, when I add the measure to the table it loads a very long time. In another table (that has some more rows, 15 to be exact) it does not work at all, after a while I receive the error message "There's not enough memory to complete this operation.".

Is there any possibility to improve the performance or maybe another solution?

[johnt75]

I think you could adapt the technique from https://www.youtube.com/watch?v=2HkBbqxBzF0