bar chart-category label- text conversion fails or at least I do not fully understand what the problem is...

The numbers {1,2,3} are not dates but integers. The text() function does not know how to turn that into a date. Check my code below

 a!forEach(
   items: {1,2,3},
   expression: text(date(2020, fv!item, 1), "mmm")
 )

Hmmm...interesting because the following test rule works without a date but with an integer:

True, as long as the only month you need is January. text(5, "mmm") evaluates to "Jan" as well. BTW, following code would work as well

index(
  {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"},
  {3,7,12,4,9,5,3},
  {}
)

True, as long as the only month you need is January. text(5, "mmm") evaluates to "Jan" as well. BTW, following code would work as well

index(
  {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"},
  {3,7,12,4,9,5,3},
  {}
)

oouch!

;)

OK. But what to do?

I like the categories to be displayed as month and the db delivers not a date but an integer...

Any idea?

(..and btw "Huhu" (Wink) :))

WORKS!

    a!columnChartField(
      categories: {
        text(date(2020, index(
          local!datasubset.data,
          "MonatAbreise",
          null
        ),1),"mmm")
      },

THX!!

You may have a look at the 'display' function too which will substitute the integers with the month abbreviation.
Und uebrigens - da ist noch ein Tippfehler im Label: es heisst wohl 'Summe der Erstattungen'