Easily proved to be the best: in every time travel story, the time traveler asks for the date. The unsuspecting drone always responds with DD or MM-DD, and the protagonist has to shout at them “NO! WHAT YEAR IS IT?”

Always start with YYYY.

I rest my case.

Gotta have that good sorting

DD is day in year, I think dd is what you mean. Also, YYYY is week year, so better to use yyyy.

yyyy-MM-dd

Anything else is madness. It’s demonstrably the only logical answer.

YMD is primarily used in:

China, Japan, South Korea, North Korea, Taiwan, Hungary, Mongolia, Lithuania, Bhutan, Sweden

That is one weird country group.

W E A R E I N E V I T A B L E