Customize date display format? [Android 7] How can I change global date format in Android 7.1.1?

I want to continue using en-US locale setting, but with ISO date format YYYY-MM-DD. And change long format into DD. MMMM YYYY (e.g. 22. october 2017).

I know that date format change is not possible via menu items in the user inferface. But perhaps is there some file in the filesystem where I can specify it?
Try en-CA locale setting.

It uses well-formed English, as well as ISO units and formats.