You "get it right" because that's the only format you see wherever you're from. It reality, it's impossible tell without context, which is why both are inferior

You "get it right" because that's the only format you see wherever you're from. It reality, it's impossible tell without context, which is why both are inferior formats. yyyy-mm-dd has the additional benefit of being sortable as text, so it's better than dd-mm-yyyy even if you ignore the obvious ambiguity.