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<div>At 18:19 -0400 30/07/09, Joshua Cranmer wrote:</div>
<blockquote type="cite" cite>David Singer wrote:
<blockquote type="cite" cite>Against that, one has to realize that
"the label of the day before X" is well-defined for the day
before the introduction of the Gregorian calendar, and iteratively
going back to year 1, year 0, year -1, and so on.</blockquote>
</blockquote>
<blockquote type="cite" cite>In neither the Gregorian nor the Julian
calendars is there a year 0, as used in conventional speech (formats
designed for machine computation treat the issue a little
differently).</blockquote>
<div><br></div>
<div>Right. I was specifically referring to Proleptic Gregorian
Calendar in the specification ISO 8601, which does. This makes
arithmetic ('how many years') and leap calculations ('is X a leap
year') simpler.</div>
<div><br></div>
<div>Wikipedia:</div>
<div><br></div>
<div>'<font face="Helvetica" size="+1" color="#000000">Mathematically,
it is more convenient to include a year zero and represent earlier
years as negative, for the specific purpose of facilitating the
calculation of the number of years between a negative (BC) year and a
positive (AD) year. This is the convention used in</font><font
face="Helvetica" size="+1" color="#002BB9"> astronomical year
numbering</font><font face="Helvetica" size="+1" color="#000000"> and
in the international standard date system, ISO 8601. In these systems,
the year 0 is a</font><font face="Helvetica" size="+1"
color="#002BB9"> leap year</font><font face="Helvetica" size="+1"
color="#000000">.</font></div>
<div><br></div>
<div>ISO 8601:</div>
<div><font size="-1" color="#000000">NOTE In the proleptic Gregorian
calendar, the calendar year [0000] is a leap year.</font></div>
<div><br></div>
<x-sigsep><pre>--
</pre></x-sigsep>
<div>David Singer<br>
Multimedia Standards, Apple Inc.</div>
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