American here. No idea. Either DD/MM/YYYY or YYYY/MM/DD are more logical, but here we are. When naming/renaming files and including a date in the name, I'll usually do YYYYMMDD format somewhere. If I'm emailing/texting others, I use MM/DD/YYYY.
Fun little story, the department I work in recently began to work with some people over in the UK, and even though I brought up the date format differences, we've already had someone of gett the month and day flipped and it caused some confusion on our end.