Re: February 30th 2000

From: J. Scott Kasten (jsk@titan.tetracon-eng.net)
Date: Wed Jan 12 2000 - 22:27:58 EST

Sorry, but no, we're not. The exact time measurement for a year
is 365.24219878... days. We round that off to 365.25 for conveininece
to get a leap day every four years. However, the decimal is less
than .25, so after 100 years, we end up ahead. Thus centuries
are not supposed to be leap years normally, in order to "down correct"
for the .25 estimate. Now, the part .00219878... remaining, works
out to be an extra day every 400 years.

Thus the rule is leap years come when the year is divisible by 4,
but not centuries, unless divisible by 400. This keeps the calendar
correct for a few thousand years.

Year 2000 happens to be one of those centuries that is a leap year.
Thus it has 29 days, since ordinary centuries would only have 28.

On Wed, Jan 12, 2000 at 11:40:05AM -0200, Daniel Lafraia wrote:
> Hi Folks,
>
> This year we're going to have the day February 30th and neither Linux, AIX,
> Windows NT, 98, 95 know this problem. Feb30th happens each 400 years (Last
> time we had that was year 1600). There's a webpage (in portuguese) from IDG
> http://www.uol.com.br/idgnow/corp/corp2000-01-10e.shl (you can translate it
> at http://babelfish.altavista.com/cgi-bin/translate)
>
> Also check out:
> http://www.isoft.itil.com/bluncal_home.htm
>
> [lafraia@cpu lafraia]$ cal 2 2000
> February 2000
> Su Mo Tu We Th Fr Sa
> 1 2 3 4 5
> 6 7 8 9 10 11 12
> 13 14 15 16 17 18 19
> 20 21 22 23 24 25 26
> 27 28 29
>
> C:\WINDOWS>date
> Current date is Wed 01-12-2000
> Enter new date (mm-dd-yy): 02-30-2000
>
> Invalid date
> Enter new date (mm-dd-yy): 02-30-00
>
> Invalid date
> Enter new date (mm-dd-yy):
>
> Does anybody know a workaround for this?
>
> See ya,
> Daniel Lafraia
>
>
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-- 
J. Scott Kasten

jsk AT tetracon-eng DOT net

"That wasn't an attack.  It was preemptive retaliation!"

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