Here are a couple of suggestions.
- For clarity, I would suggest to split #004 into two parts: #004 for
intervals containing "date / date" and #005 for intervals containing "date
- In the "examples" column, all "date / date" intervals are symmetrical,
that is with year-year, month-month or day-day precision. In the "rules"
column, other constructs are described, where the year (and sometimes even
the month) is removed. I consider that symmetry (in this context) has the
advantage of clarity and that other constructs (if we want them) should be
described in detail when it comes to their semantics.
- According to the "rules" column, it is not clear whether we should write
which I consider could be shortened (and canonicalized) as
where M's and D's are assumed to be zero when absent from such a context.