Was looking for this. Yes. Whenever possible, dates should be specified in a format that is BOTH RFC 3339 and ISO 8601. I'd say both have their quirks, but the intersection of the grammars is machine-parseable and human-readable without (much) legacy baggage or (much) experimental / reserved-for-future-use noise.

Though the way it specifies raw UTC times is odd (8601 uses Z, 3339 uses -00:00), that got changed with RFC 9557 to align with 8601.

It also supports "zoned date times", where instead of just using the UTC offset, you can also include a timezone identifier, e.g. 2020-01-01T00:00+01:00[Europe/Paris]. Useful if you're doing calculations on dates but can be ignored otherwise.