I would like to make a new suggestion about the calendar issue.
> "'gregorian' is the only value defined."
This raises the question whether:
(implying "astronomical" numbering) is to be considered the same as
or if negative years can not and never be assigned a calender (as of
today's EDTF specification).
I suggest to move the whole concept of "calendar" to EDTF phase two and in
today's EDTF phase one, refer to ISO_8601 and only state that the
"astronomical numbering" is default.