Dax with relative date

[DJ1977]

Hello. 

I would have greatly appreciated if someone could help me with a dax formula for the following case:
I have a dimension table for product, a fact table for sales and a calendertable.  Relevant tables:

The products are food and have a shelf life. The different products have different shelf lives. I have this DAX that calculates how many customer have purchased the selected products within the shelf life (duration time) based on today's date:

# Customers Purchased in Shelf life =
VAR Last_date = TODAY()
VAR Shelf = SELECTEDVALUE(DimProduct[ProductShelflife])

Return
CALCULATE( DISTINCTCOUNT(FactSales[CustomerID]),
FILTER( ALL(DimCalendar),
DimCalendar[Date] > Last_date - Shelf &&
DimCalendar[Date] < Last_date))

Now i want to add a relative date filter in my report so that the users can for example choose last 2 weeks and then see if the product is purchased within the last two weeks, insteed of the shelf life date. I assume i have to make Dax to be calculated with the selected filter instead of VAR Shelf. How can i adjust my DAX to achieve this? If the relative date filter is blank, i want the dax to use VAR Shelf.

I'd really appreciate some help here

[AlexisOlson · Accepted solution]

Can you just use DimCalendar instead of ALL ( DimCalendar ) or is there some local filter context that prevents that from working?

Quantity Purchased Shelf life =
VAR Last_date = TODAY ()
VAR Shelf = SELECTEDVALUE ( DimProduct[ProductShelflife] )
RETURN
    CALCULATE (
        DISTINCTCOUNT ( FactSales[CustomerID] ),
        FILTER (
            DimCalendar,
            DimCalendar[Date] > Last_date - Shelf
                && DimCalendar[Date] < Last_date
        )
    )

If that doesn't work, you could try ALLSELECTED instead of ALL.

[DJ1977]

The removal of All solved my case. Thank you so much for the quick response @AlexisOlson 👍