The specification lists ordinal date format YYYY-DDD as a valid value.

If by parsing the "value" element(s), at least a specific date has been found, then the "value" is overall valid, and the parser assembles the overall datetime value by concatenating the specific date, " " (space character) and specific time (if time was specified, with 00 minutes implied if no minutes are provided), and specific timezone (if timezone and a specific time was specified).

My reading of this^ section is the ordinal date format should be preserved in the assembled datetime. I wanted to confirm that's correct, though, since the only results listed are YYYY-MM-DD variants:

• YYYY-MM-DD - no time specified
• YYYY-MM-DD HH:MM or YYYY-MM-DD HH:MM:SS - time specified but no timezone. This is a floating time.
• YYYY-MM-DD HH:MMZ or YYYY-MM-DD HH:MM:SSZ or
• YYYY-MM-DD HH:MM-XXYY or YYYY-MM-DD HH:MM:SS-XXYY or
• YYYY-MM-DD HH:MM+XXYY or YYYY-MM-DD HH:MM:SS+XXYY - both time and timezone offset were specified.

If it should be preserved, I'd recommend we add some examples to that list.