Have you tried to have a look at the Qlik Sense Help?
Here is the link where you can find answer how to change language in Qlik Sense.
Norwegian is not a supported language (in that the user interface is not currently translated into Norwegian). - and so the UI falls back to the default language - English-US.
This is not an actual error as such, and there's probably no need for the message to be logged to the console at all.
What issues are you seeing with date formatting? - are you still seeing them?