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On Tue, 14 Dec 2010 09:10:51 +0000, Simon Grant wrote 
> I'd say best to avoid notations which people want to use in divergent ways. 
> Personally I rather like your idea, Ray, about x being used in the
indication of the set of all numbers with x replaced with 0..9, but we don't
really need it, and if others think it should mean something else, well I'd be
happy to do without it.

x as [0-9] implies always a precision of year. 
19xx would then be 1900/1999 (with a precision of year) 
which contrasts with the  20th century ( {1901-2000} with a precision of  100
years)

What we could do to keep the syntax sound ( and thus  give a unique meaning to
19xx):

19xx as {1900-1999} with a precision of 100 years 
19   as 20th century , e.g. {1901-2000} with a precision of 100 years.

BUT with the additional condition that  "aprox", resp. "unknown" applied to
19xx  and 19 are  equivalent: 
    19xx~  = 19~ 
    (19xx)? = (19)? 
     
I think this makes logical sense since  the difference between  the two is
an offset of 1 year, a magnitude  under the precision of our dates.

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