Comment by 8organicbits

I think modern browsers are actually quite good here. They show a template in the form TT.MM.JJJJ for me (so the German equivalent of MM/DD/YYYY, with the usual order and separator in German). I can just type the date, including the dots if I want (they're just ignored; there would be extra points for moving me to the next component when typing "2.", but the world's not perfect). If I'm confused about the format, or want to see a calendar view, I can click on the calendar icon (also accessible via tab) and select a date there.

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).)

I don't even know my locale.

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 mean, once in a different country, you either experience the locale shock once then adapt, or you've seen it before and kind of know what to expect.

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.