> It is important that a Norwegian visitor with a browser configured to prefer en-US [1] would see the entire web page in the same locale. Why should _parts_ of the web page localize to a different locale than other parts?
Completely agree - that should not happen. Consistency is most important. So if a Norwegian user has an en-US browser and the rendering uses this control which uses default browser locale then all date rendering in all markup has to be en-US. That is: this control can't be used on a web site unless the site already uses browser locale for all date input and output.
If the web page already has custom date formatting (e.g. the user chooses locale/format in the site preferences) or if the page has elements rendererd DD.MM.YYYY already from the back end - then this control can't be used.
(Also: TIL Norway doesn't use ISO 8601 like Sweden. I honestly thought ISO 8601 was norm in Europe, but apparently mostly in Sweden).