From owner-freebsd-hackers  Mon Aug 17 08:36:13 1998
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Date: Mon, 17 Aug 1998 15:30:28 +0000
From: "Kaleb S. KEITHLEY" <kaleb@ics.com>
Organization: Integrated Computer Solutions
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To: hackers@FreeBSD.ORG
Subject: WRT y2k compliance, in 2000, the day after Feb 28 is NOT Feb 29.
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All this talk about y2k stuff, consider the following:

#include <sys/types.h>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>

int main ()
{
    time_t feb28;       /* 28 Feb, 2000, 23:59:59 */
    time_t mar1;
    struct tm tm_feb28; /* 28 Feb, 2000, 23:59:59 */
    struct tm* tm_mar1; /* 1 Mar, 2000, 00:00:00 */

    tm_feb28.tm_sec = tm_feb28.tm_min = 59;
    tm_feb28.tm_hour = 23;
    tm_feb28.tm_mday = 28;
    tm_feb28.tm_mon = 1;
    tm_feb28.tm_year = 100;
    tm_feb28.tm_isdst = -1;  /* for POSIX mktime to DTRT WRT DST */

    feb28 = mktime (&tm_feb28);
    (void) printf ("%s\n", ctime (&feb28));

    mar1 = feb28 + 1;
    (void) printf ("%s\n", ctime (&mar1));

    tm_mar1 = gmtime (&mar1);

    (void) printf ("month (s/b 2):%d\n", tm_mar1->tm_mon);
    (void) printf ("  day (s/b 1):%d\n", tm_mar1->tm_mday);

    return 0;
}

I ran this program on:
  SunOS 4.1.4, 
  Solaris 2.5.1 
  Solaris 2.6
  HPUX 10.20 
  IRIX 5.3
  IRIX 6.2
  Digital Unix 3.2
  Redhat Linux 5.0 (libc6/glibc 2.0.7)

and they all got it wrong. (It could be that one or more of them are
fixed in some patch I don't have installed. <shrug>) I didn't try on
FreeBSD because that's at home, but I'd be willing to wager serious
money that it gets it wrong too.

And I didn't check, but if they all think 2000 has a 29 Feb., then I'd
wager they think that there's 366 days in the year too, and that all the
day-of-the-week are off by a day for every day after Feb 28.
/usr/bin/cal is broken too on the two systems I checked.

-- 
Kaleb S. KEITHLEY

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