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Re: Internal inconsistency wrt year 0000

From: James Clark <jjc@jclark.com>
Date: Thu, 25 Apr 2002 15:09:49 +0700
Message-ID: <016001c1ec30$91e788a0$3500a8c0@bkk.thaiopensource.com>
To: "Ashok Malhotra" <ashokma@microsoft.com>, <www-xml-schema-comments@w3.org>
Cc: "C. M. Sperberg-McQueen" <cmsmcq@acm.org>
It's not equivocal if you want to allow negative years.  If you allow
negative years, you have to allow 0.  There is nobody that makes -1
correspond to 1 BC. WikiPedia isn't authorative but I gave you many
references and they all support the same conclusion.

Certainly there is no justification for claiming ISO 8601:2000 is incorrect,
and thus no chance of ISO 8601:2000 changing to make -1 correspond to 1 BC.
Surely it is an intolerable situation for both W3C Schema and ISO 8601 to
allow -0001 but for each to give it a different meaning.

James

----- Original Message -----
From: "Ashok Malhotra" <ashokma@microsoft.com>
To: "James Clark" <jjc@jclark.com>; <www-xml-schema-comments@w3.org>
Cc: "C. M. Sperberg-McQueen" <cmsmcq@acm.org>
Sent: Wednesday, April 24, 2002 11:08 PM
Subject: RE: Internal inconsistency wrt year 0000


> James,
> I looked up the reference you cited in the WikiPedia and it is
> equivocal.
> It says:
> "When using the Latin numbering system, which does not include zero, it
> is traditional to represent the years preceding 1 as "1 BC" etc.  In
> this system the year 1 BC is a leap year (likewise in the proleptic
> Julian calendar).
>
> When using a numbering system which includes zero, it is more convenient
> to include a year zero and represent earlier years as negative. This is
> the convention used in the "astronomical Gregorian calendar". In this
> system the year 0 is a leap year."
>
> So, it seems you may or may not allow year zero.  We could choose to
> conform
> to ISO 8601 and allow year zero or not.
>
> Also, is WikiPedia an authoritative source?
>
>
> All the best, Ashok
> ===========================================================
> Ashok Malhotra              <mailto: ashokma@microsoft.com>
> Microsoft Corporation
> 212 Hessian Hills Road
> Croton-On-Hudson, NY 10520 USA
> Redmond: 425-703-9462                New York: 914-271-6477
>
>
>
> -----Original Message-----
> From: James Clark [mailto:jjc@jclark.com]
> Sent: Tuesday, April 23, 2002 7:37 PM
> To: Ashok Malhotra; www-xml-schema-comments@w3.org
> Subject: RE: Internal inconsistency wrt year 0000
>
>
> > Our current thinking is that ISO 8601 is in error and we want to
> request
> > a change disallowing the year 0000.
> >
> > You said:
> >> Now the year 1BC in the proleptic Gregorian calendar is a leap year.
> >
> > Where can I confirm this information?  We've been worrying about a
> > related change in the comparison of durations that is affected by this
> > information.
>
> If you start from first principles, I think this has to be the case.
> The
> purpose of leap years in a calendar is to ensure that the mean length of
> a
> year in the calendar is as close as possible to the length of the solar
> tropical year.  This requires that the calendar have a regular cycle.
> The
> cycle of the Gregorian calendar is 400 years.  The year 400AD is a leap
> year. The year 1BC immediately precedes 1AD and so is 400 years before
> 400AD. Therefore 1BC must also be a leap year.  In other words, if 1BC
> was
> not a leap year, there would be a discontinuity in the proleptic
> Gregorian
> calendar for which there is no justification.  I did a bit of googling
> and
> found the following:
>
> http://www.bluewaterarts.com/calendar/InterGravissimas.htm  (translation
> of
> Papal Bull establishing the Gregorian calendar)
> http://www.wikipedia.com/wiki/Proleptic+Gregorian+Calendar
> http://serendipity.magnet.ch/hermetic/cal_stud/cal_art.htm#Astronomical
> http://astro.nmsu.edu/~lhuber/leaphist.html
>
> As regards the the year 0000 issue, everything I have found on the Web
> suggests that ISO 8601 is correct, and that the year -1 corresponds to 2
> BC
> not 1 BC.  There are two ways to number years:
>
> -2, -1, 0, 1, 2
> 3 BC, 2 BC, 1 BC, 1 AD, 2 AD
>
> but never
>
> -2, -1, 1, 2
>
> In addition to the above see:
>
> http://webexhibits.org/calendars/year-definitions.html
> http://www.znaturforsch.com/df/gc.htm
> http://www.maa.mhn.de/Scholar/calendar.html
> http://webexhibits.org/calendars/calendar-christian.html
>
> I have never found anything that suggests that the year -1 corresponds
> to 1
> BC in the Gregorian calendar.
>
> James
>
> > All the best, Ashok
> > ===========================================================
> >
> >
> > -----Original Message-----
> > From: James Clark [mailto:jjc@jclark.com]
> > Sent: Tuesday, April 23, 2002 6:30 AM
> > To: www-xml-schema-comments@w3.org
> > Subject: Internal inconsistency wrt year 0000
> >
> > The inconsistency between XML Schema Part 2 and ISO 8601:2000 wrt year
> > 0000
> > has already been commented on, but there is also a minor internal
> > inconsistency.  XML Schema Part 2 disallows year 0000, which means
> that
> > year -0001 corresponds to 1BC (whereas in ISO 8601:2000, 1BC is year
> > 0000).
> > Now the year 1BC in the proleptic Gregorian calendar is a leap year.
> > However, appendix E uses the formula
> >
> >   modulo(Y, 400) = 0 OR (modulo(Y, 100) != 0) AND modulo(Y, 4) = 0
> >
> > to determine whether Y is a leap year.  But this formula makes year
> > -0001
> > not a leap year.  If year 0000 was allowed (representing 1BC), then
> the
> > formula would be correct.
> >
> > James
> >
> >
>
>
>
>
Received on Thursday, 25 April 2002 04:10:04 GMT

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