From: Edward C. Zimmermann
> But why not "later"? "Never" is not possible since it embodies such
> strong certainty. And if one knows with certainty that it can't ever be
> filled in..

Why does it have to be one or the other, i.e. "will be filled in later" or
"will never be filled in". Why can't it be "might be filled in later"

> A "standalone" date such as 2001-1u-u8 ... what do the "u"s here mean..

This is not intended to be allowed - an incomplete part of a date component
- year, month, or day - occupied by u(s) with the rest filled in. I've seen
no use case for that. 

> what does the expression say? A date such as 2001-uu-12 is saying that
> an event took place on the 12th day of a month to be filled in later in
> the year 2001.  

Why can't it say "12th day of an unspecified month which might be filled in

> In "standalone" dates the expressions 2001-12-uu and 2001-12 are not
> the same. They have different precision and are telling different
> stories..
That's fine, I have no problem adding a note about precision to this effect.

> The confusion comes as soon as we let "u" be anything other than a
> placeholder "to be filled in later".. Why a placeholder has been used
> instead of using a digit or a digit and an expression of
> approximateness or uncertainty (using one of our postfix unary
> operators) is beyond the scope of our concerns and does not matter..

I would assert that going beyond "might be filled in later" and expressing
certainty that it will be filled in later is beyond our scope.