Why are all time&dates in English?

Ive always wondered how to get HA to show my time and dates in my locales language. I’ve set the correct timezone in configuration.yaml, and use the correct language in the frontend.

Still all my days, months and dates are in English, no matter what I try. Is there another setting needed for this?

    friendly_name: Vandaag
    entity_id: sensor.date
    value_template: >
      {{ now().strftime("%A %d %B %Y") }}


Most dates are outputted as ISO 8601 because otherwise it would become hard to make calculations.

thanks, I understand that. But there is no way the HA frontend can translate these, like all the other values, names and states? Couldn’t the language setting be used for that, without interfering with the fundamental calculations?