"Hammer this into the ground" sounds unwarrantedly rough, but, well, let's try to finish the discussion positively...
195u means the event took place in the 1950s (its unit of precision is 10 years)
19uu means that the event took place in the 20th century (its unit of precision is 100 years)
1uuu means that the event took place in the second milennia (its unit of precision is 1000 years)
uuuu means that we don't know when the event took place[...]
But the 'u' delivers more:
uu59 means that we know the event took place in the year 59 but don't know the century
1u59 means that we know the event took place in the year 59 in the second milennia but don't know which century.
The extended date system has not provision at this time for |.
> However, in both cases this states a claim or belief that the actual value
is one of the set running all the way from 1980 to 1989. I don't see any
*pragmatic*, *operational* reason for making a distinction. Furthermore, I
believe that if such a distinction were made, in practice people would argue
over or confuse the two, leading to inconsistency of semantics. The
consequence would be that in practice, both forms would have to be treated
equally in any case.
In our systems (matching and searching dates) we would all probably handle
them as the same but the sentence
But.. just to hammer this into the ground...
195u is expressing something known (1950s)
195| is expressing more: Not only is it known that the event took place in the
1950s but we claim to be able (at some future time) to increase the precision.
195| is essentially claiming a year precision but expressing that the year is
not yet collected. Its a kind of "volatile" flag announcing that the precision
might increase at some future time.