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From: neal@druhi.ATT.COM (Neal D. McBurnett)
Newsgroups: comp.sys.ibm.pc,comp.sys.atari.st
Subject: Re: Will Your SW Make it to the year 2000?
Message-ID: <4345@druhi.ATT.COM>
Date: 23 Jun 89 19:19:34 GMT
References: <4342@druhi.ATT.COM>
Organization: AT&T Bell Labs, Denver CO
Lines: 33

in article <4342@druhi.ATT.COM>, terrell@druhi.ATT.COM (TerrellE) says:
> I was amused to find that allegedly state of the art scheduling software, 
> TimeLine, is broken for the year 2000.  So is MS DOS.
> 
> The Gregorian calendar reform makes every year evenly divisible by 4 a
> leap year EXCEPT for century years.  Consequently there is no January 29,
> 2000.

No, no, no.  First, of course, every year has a January 29th.  I'll assume
we're talking about Feburary 29th.

Second, the Gregorian calendar says that
	years divisible by 4 are leap years, except,
	years divisible by 100 are NOT leap years, except,
	years divisible by 400 are leap years.

Either the Gregorian calendar or more recent proposals have suggested
these refinements:
	years divisible by 4000 are NOT leap years.
	years divisible by 20000 are leap years.

This makes the calendar keep in step with the tropical year for about the
next 150000 years.  A tropical year is 365.242194 days or so.

I'm not sure, though, to what extent this might be affected by our more
recent knowledge of the rate of change of the length of a year.  I guess
that the periodic addition of leap seconds makes the year average out to
the proper value for use in the above calculations....

Anyway, the year 2000 is a leap year, and software developers are safe until
2100.

-Neal McBurnett, neal@druhi.att.com or att!druhi!neal