Are millenniums allowed?

[OtterSou]

On my copy of ISO 8601-1:2019, I don't see any mention of milleniums. Your table (specifically 2) says it's allowed, but I don't think so.

[IJMacD]

Yes thank you for raising this issue.

I looked into it and I think I made an assumption based on § 5.2.2.2 Representations with reduced precision. Earlier drafts gave examples reducing precision down to centuries but gave no indication whether decades or millennia were supported.

I think I'll need to update the diagram and table.

Thanks.

[Crissov]

Just for the record, EDTF Level 2 in ISO 8601-2 supports stuff like 2XXX (unspecified digits) and Y2E3S1 (exponential year with significant digits) to represent any year in a particular millennium.