Ah, I guess season is for string representations.
Why we need to annotate this schema!
Part of what we need to settle, though, is what features of EDTF we support, and what we don’t.
Looking more closely at the spec, I think we do want the Level 1 feature “Qualification of a date (complete),” but we do not want the Level 2 extension “Qualification of Individual Component.”
That would keep the two date representations consistent, and simplify implementation.
In that case, probably the sensible path is to follow biblatex, and say we support levels 0 and 1, with the same approach to uncertain dates (though we need more feedback from others on the X feature, which biblatex does support).
Even if coupled with the existing “circa”?
Actually circa = EDTF approximate, so we need a new “uncertain/isUncertain.”