Xref: utzoo comp.sys.ibm.pc:31172 comp.sys.atari.st:17632
Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cmcl2!rna!amms4!hjg
From: hjg@amms4.UUCP (Harry Gross)
Newsgroups: comp.sys.ibm.pc,comp.sys.atari.st
Subject: Re: Will Your SW Make it to the year 2000?
Message-ID: <441@amms4.UUCP>
Date: 7 Jul 89 14:37:09 GMT
References: <4342@druhi.ATT.COM> <381@amms4.UUCP> <382@amms4.UUCP>
Reply-To: hjg@amms4.UUCP (Harry Gross)
Organization: Eagle Clothes, Inc., New York, NY
Lines: 49

In article <381@amms4.UUCP> I wrote:
>is just a wee bit more than that stated above.  Specifically, a leap year
>exists if:
>
>		1) the year is divisible by 4 AND
>		2) the year is NOT divisible by 400
>
>thus, the years 1700, 1800 and 1900 were leap years, but 2000 will NOT be
>a leap year, and 2100 WILL be.

In article <382@amms4.UUCP> I modified that to read:

>rule 2) should state:
>
>2) the year ends in 00 and is NOT divisible by 400
>
>also, the AND at the end of rule 1) should be an OR.
>
>Thus:
>1) the year is divisible by 4 and does NOT end in 00  OR
>2) the year ends in 00 and is NOT divisible by 400

In a private message from neubauer@bsu-cs.bsu.edu (Paul Neubauer), he wrote:

>You have the century years backwards!  1700, 1800, and 1900 were NOT leap
>years, but 2000 will be.  No flame, just a warning:  check this algorithm
>BEFORE you code it into something that might be around for very long.

I replied to him that I was fairly certain that I had it right, but that I would
check anyway.  Well, I had it wrong (open mouth, insert foot, close mouth :-)

Paul was right, and I _did_ have the centuries backwards.  A correct test for
leap year, therefore, is:

	if (year%4 == 0 && year%100 != 0 || year%400 == 0)
		printf("LEAP YEAR!");

That test comes from the K & R book, from their date conversion routine
somewhere around page 103 (113?).  I should have looked before I leapt :-)

Sorry for the unnecessary noise, but I did want to post the correction (and
the apology :-).

		Later,
-- 
		Harry Gross				 |  reserved for
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