calendar month names

Greg 

First, thanks for your reply! much appreciated.

Allthough it didn't solve it. Here is example of what it now looks like. I have a DATE column, of which i can't change the name to Dutch DATUM , so i created a DATUM column as well based on DATE.

Then the month number, and then i want the long month name (januari / februari etc, being dutch names)

So you can see the DAX i used to create the long month name. As said its the English name, where al settings are in Dutch. And its the wrong name too, as December is put to month 1, while January is put on the other months. 

I used this DAX before but never experienced this tbh. So i have no clue where to look for the solution.

Well i can create a new table with month numbers and month names in dutch , and then somehow link this to calender. But that should not be the way to go imo.