There's a special URL type because URLs are not strings, and the computer needs to know that. The date format is not ISO8601 because ISO8601 has too much cruft

There's a special URL type because URLs are not strings, and the computer needs to know that. The date format is not ISO8601 because ISO8601 has too much cruft, bad defaults, and is missing real timezone data. I'd have been fine with the cruft and bad defaults, but lack of timezones is a deal breaker.