American software engineers use ISO8601 or RFC3339 ... I just wrote 20210108 in my journal this morning (referring to a podcast episode published yesterday).
I'll admit I might be annoying to others ... my wife is specifically irritated when I write a time in military format (but my son has no problem reading it from my phone).
> I am pretty sure that most of South East Asia (dunno about India and Nepal) use YYYY/MM/DD.
I think you might have meant East Asia. I know Japan primarily uses YYYY/MM/DD.
Singapore, Malaysia, Indonesia, Thailand, Vietnam, Cambodia, Laos, Myanmar, etc (South East Asia) conventionally use DD/MM/YYYY. Interestingly, the Philippines seems to use MM/DD/YYYY.