ISO 8601 contains way too many obscure formats. RFC 3339 is pretty much a subset and defines only sensible ones. It also allows 2018-02-05 08:02:43-00:00 (no T and explicitly specifying no timezone)
Acquiring the document (legally) to ensure compliance for ISO 8601 is relatively expensive for a single person (~$200 USD), while RFC 3339 is accessible for free.
Disregard ISO8601. Acquire RFC3339. You can leave off the T if you want to, or replace Z with
+00:00.https://ijmacd.github.io/rfc3339-iso8601/
with ISO 8601:
https://discuss.tchncs.de/comment/10487289
Acquiring the document (legally) to ensure compliance for ISO 8601 is relatively expensive for a single person (~$200 USD), while RFC 3339 is accessible for free.