Is is the device display language, the keyboard input language, my geo location, my browser language, my legal location, my browser-preferred website language, the language I set last time, the language of the domain (looking at amazon.co.uk), the language that was auto-selected last time for me on mobile or... something else entirely?
I don't normally run Windows, so I can't check right now, but I think it's mostly "modern" applications that mess this up. Like the MS Store, Teams (obviously).
For normal date inputs, I really don't think there is a good reason to use anything else. (Possible exceptions I can think of: Selecting date ranges and/or showing extra data about the dates (like daily prices).)
https://stackoverflow.com/questions/7372038/is-there-any-way...
And for the rest of the users who have no idea about locales, using whatever locale they have on their computer might be technically incorrect for some of them, but at least they're somewhat used to that incorrectness already, as it's likely been their locale for a while and will remain so.
Think about traveling to a different country for a limited time. I want my location, time zone, etc to be set to where I am. I traveled across the US a few years ago, and I would rather not have to mentally follow in which time zone I was. Heck, I don't even know where the limits are. Bonus points for DST happening on a different date than in Europe, and extra bonus for there being no DST in Arizona, except for Navajo Nation? I remember signs saying it was illegal to carry alcohol, but I don't recall anything about time zones.
But as a European, I don't want my date to suddenly appear in US format; I'm only there for a few weeks.
Not really. A lot of computers are set to US locale (probably because it's the default) and the user just has no idea why some programs have dates in some crazy middle-out format and avoids those programs.
