On Thu, 23 Dec 2010 12:56:15 -0500, Ray Denenberg wrote
> Ed Said:
> "The 20th century using year precision is an interval covering 1901 to the end of 2000."
> But it seems that Gerard and Simon (and perhaps others) don't agree with you on that defintion of the 20th century. So if we have some way to denote "20th century" then at best we would have to leave it unspecified what exact period we are denoting.  Further, how would we denote it?    We (mostly) agree that '19' should mean 1900 through 1999, so we can't use '19', we would need another representation. But then, ISO seems to imply that '19' means "20th century" (without defining it).  This is all very convoluted, isn't it?
Yes. Early ISO 8601 even called CC in CCYY century but dropped it due to the silly realization that 2000 was not in the 21th century in the Georgian system.

We agree that a century is 100 years. We agree that CC00 years are centurial years
(e.g. 1900, 2000 etc). The question is when does a century (in day precision) start
and where does it end. The Georgian calendar defines it clearly (as 01-00) and the
Astronomical year number systems define it also clearly (as 00-99). The fundamental
problem is that the Christian calendars don't have a year ZERO.

The solution then would be to define calendars-- recall we had a slot for Georgian
and Julian. I suggest, for now, the term astronomical and to make everyone happy
that instead of Georgian as our default calendar--- the basis for ISO 8601-- that we
use astronomical. Atronomical has the interesting advantage that is also "swaps"
between Julian (dates before 1582) and Georgian (dates after 1582) and better
represents, I think, bibliographic dates as provided in their publication. This has
also the advantage that it has a year Zero (which while defined is ISO 8601 is not
defined in either of Julian or Georgian calendars).


Edward C. Zimmermann, NONMONOTONIC LAB 
Basis Systeme netzwerk, Munich Ges. des buergerl. Rechts 
Office Leo (R&D): 
 Leopoldstrasse 53-55, D-80802 Munich, 
 Federal Republic of Germany 
Umsatz-St-ID: DE130492967