The important part is agreeing both %D-%M-%Y and %M-%D-%Y are wrong
Learned from poking around this that RFC 3339 can’t be used to represent dates before 1 BC. (1 BC itself is fine, since the production for date-fullyear is 4DIGIT, so 0000 is acceptable. -0001, which in ISO 8601 represents 2 BC, is not.) Also has a Y10k problem.
Dates before the Gregorian calendar aren’t well defined anyway. If you’re doing astronomy, there’s a separate Julian calendar for it, but it’s not ISO.
I love this visualization.
It’s a shame ISO 860 insists on that stupid T.
Truly, old molehills make the best mountains.