>YYYY-MM-DD is a much better choice. It sorts like a number

Not sure I disagree. Sure the sorting by numbers is of interest to the HN crowd but has little value to anyone outside of IT.

In most cases I'm most interested in the "day" part so its convenient if thats first (which it is in 90% of the world).

It's the standard in Japan at least.

The best part of YYYY-MM-DD is that almost nobody uses it, so it'll be easier to get everybody to support. I don't think we can standardize in either DD-MM-YYYY or MM-DD-YYYY.