Set locale the kirby way

Hi there,
I have problems setting the correct locale for dates. It’s not a multilanguage setup.
In my config I have set

return [
    'locale' => 'de_DE.UTF-8',
    'date.handler' => 'strftime'

But this doesn’t change anything. If I add before this return the php setlocale(LC_TIME, 'de_DE.utf-8'); it works as expected.
This also translates the dates in the panel properly.

But why is the kirby-way not working?

Not working on the frontend or in the Panel?

There was an issue regarding the API ignoring the configured locale for single-language sites, that should now be fixed on the dev branch. But that shouldn’t affect the frontend. And in my test it works as expected with dates.

Do you happen to have more than one return array in your config?

It doesn’t work in the frontend and the panel.

in the config file is just one return array.

In the frontend it worked, but all of a sudden it switched back to english. Sometimes it doesn’t work an my local machine. but normally it is fine on the production server.

But at least it works with setlocale().

Hm, inconsistent behaviour is strange. And you haven’t made any changes to your local environment? Does this also happen when using a fresh Starterkit? Are you using any plugins that might interfere somehow?