Comment by vladvasiliu

Exactly. Under Windows, this isn't even consistent across applications. I'm in France, with the location set to France, using English display language and "English (Europe)" formatting. This means that the expected date is DD/MM/YYYY. It's what shows up in the taskbar, for example. But many applications seem to do this based on language, so I sometimes get MM/DD/YYYY.

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).