A lot of this discussion has been beyond me in terms of formal logic and technical specifications, but I agree with much of what Stephen Davis said.

I think for most purposes in the bibliographical world, if not all, it doesn't matter if the 20th century began in 1900 or 1901. A century is a very loose concept and any attempt to define it for metadata has to accept that looseness. For some purposes, "twentieth century" could mean the period from the start of World War I to the fall of the Berlin Wall. Or maybe it ended for cultural/political purposes on 9/11/2001. But usually it means an imprecise period from about 1900 to about 2000, and whether you start counting at the beginning or end of 1900 doesn't matter.

I don't think the solution in ISO 8601 is particularly elegant, but I understand the need to use that standard whenever possible.

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John Hostage Authorities and Database Integrity Librarian
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> -----Original Message-----
> From: Discussion of the Developing Date/Time Standards
> [mailto:[log in to unmask]] On Behalf Of Ray Denenberg, Library
> of Congress
> Sent: Wednesday, January 05, 2011 18:08
> To: [log in to unmask]
> Subject: Re: Comments on draft edtf specification
>

> > 4.) Unspecified years, days, and months can be represented with the
> > letter u.  From the examples: 199u, 1999-uu, 199901uu.  However, when
> > only the century is known, the letter u is not used to fill in the
> > missing digits: 19 is used for sometime in the 20th century.  It
> seems
> > like if we're going down the path of using the letter u, we might as
> > well use it in the century coding (19uu) as well in order to be
> > consistent.
>
> Actually, no, '19' would not mean "SOMETIME in the 20th century" it
> would
> mean "THE 20th century".
>
> There has been a great deal of discussion of this and surrounding
> issues but
> let me start out by saying that the only reason why in our spec '19'
> means"the 20th century" is that that's what it means in ISO 8601, and
> one of
> the principles of this work is that whatever we want to express, if it
> is
> expressible in ISO 8601 then this spec should at least specify that
> syntax
> even if it perhaps specifies alternative syntaxes not specified in ISO
> 8601.
>
>
> The case of century is particularly troubling because we cannot even
> agree
> what it means. Some of us believe that the 20th century began in 1901
> and
> others believe it began in 1900. ISO 8601 doesn't help resolve this
> because,
> even though it tells you how to represent a century, it doesn't tell
> you
> what a century is. And it is fairly clear to me that we are not going
> to
> agree to a definition and are going to have to leave it undefined.
>
> But there is a way to represent the interval consisting either of the
> years
> (1) 1900 through 1999, or (2) 1901 through 2000:
>
> (1) 1900/1999 or 1900--1999
> (2) 1901/2000 or 1901--2000
>
> So I think we should keep '19' in the spec to mean "19th century"
> (undefined) for reasons I stated above, with the general guidance that
> if
> you have a specific interval you want to represent you'd be better off
> using
> one of these two forms. If on the other hand you want to designate
> during
> what century World War II occurred, '19' is probably good enough.
>
> But I digress from the point you raised. The spec would indeed support
> '19uu' to mean "some unspecified year between 1900 and 1999". If what
> you
> want to say is the event occurred "sometime during the period between
> 1900
> and 1999" -- it is a matter somewhat outside the scope of the spec to
> say
> whether 1900/1999 means
> (1) an instant in time during that period, or
> (2) the entire interval
>
> That would be a semantic matter for the applcation which references the
> spec
> to specify.
>
> I hope this helps. Thanks again.
>
> --Ray