O> I think I found one omission: The value from "month" in the Type O> 2(+) packet header is "0-11 for Jan-Dec" (in contrast to 1-31 for O> "day" of month). This isn't mentioned in Stephen's draft.
I believe that is a consequence of time.h and has nothing to do with fidonet. It is all in the localtime() structure that 0-11 for months was used rather than the 01-12 used for months in strftime() which is also part of time.h. According to c89 standards output for strftime does include enough % specifiers to output proper iso-8601 or even a rfc-3339 formatted datetime stamp. For sure "2021-02-13 14:06:58 +0000" is doable and is backwards compatible to c89. We could have been using a four digit year since day one.
Life is good, Maurice
... Þæt folc bið gesælig... and gesundful þurh gesceadwisne reccend.