I believe internationally that YMD and DMY are the two most common formats (and also the most logical), and the (much less logical) MDY comes third… YDM is a very distant fourth. MYD, DYM are theoretically possible but doubt anybody uses them

Actually, although MDY is by far most common in the US, I’ve seen US federal government forms that use DMY instead (although I imagine that’s rare, I’m sure you’ll find DMY US govt forms are greatly outnumbered by MDY ones)

I had never seen Y/D/M. I almost never see American use Day/Month order to begin with, let alone Y/D/M.