[PHP-DEV] PHP 4.0 Bug #6781 Updated: Error in mktime() funtion (Serious???) From: Bug Database (php-dev <email protected>)
Date: 09/17/00

ID: 6781
Updated by: derick
Reported By: landen <email protected>
Status: Closed
Bug Type: Date/time related
Assigned To:
Comments:

You just discovered daylight savings time.... closing

Previous Comments:
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[2000-09-17 01:52:01] landen <email protected>
OK, I found out that it was just Daylight Savings Time!

I wish I could just delete this message so my stupidity won't be displayed so publicly ;)

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[2000-09-17 00:56:01] landen <email protected>
It seems there are dates that have more and dates that have less seconds, try this quick and dirty code (I pretended all months have 31 days):

  echo "<pre>";
  for ($year=2000; $year < 2005; $year++) {
    for ($month=1; $month <= 12; $month++) {
      for ($day=1; $day <=31; $day++) {
        $diff=mktime(0,0,0,$month,$day+1,$year) - mktime(0,0,0,$month,$day,$year);
        if ($diff != 86400) echo "$year/$month/$day has $diff secondsn";
      }
    }
  }

Results:

2000/3/26 has 82800 seconds
2000/10/29 has 90000 seconds
2001/3/25 has 82800 seconds
2001/10/28 has 90000 seconds
2002/3/31 has 82800 seconds
2002/10/27 has 90000 seconds
2003/3/30 has 82800 seconds
2003/10/26 has 90000 seconds
2004/3/28 has 82800 seconds
2004/10/31 has 90000 seconds

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[2000-09-16 23:41:31] landen <email protected>
I was using the mktime function to calculate the number of days between two dates by dividing the difference by 86400 (the number of seconds in a day) when I stumbled across this one (my code came up with fractional results):

  echo "2001/03/25: has ",mktime(0,0,0,3,26,2001) - mktime(0,0,0,3,25,2001)," seconds<br>";
  echo "2001/03/26: has ",mktime(0,0,0,3,27,2001) - mktime(0,0,0,3,26,2001)," seconds<br>";

It seems PHP thinks the number of seconds in 2001/3/25 is 82800!!!

I'm not sure if this could be a bug in a library, but it even occurs on an ancient Slackware installation. I tried the same in Perl using the POSIX module which comes up with the right answer.

Now, to confuse me even more MySQL seems to have the same bug, try this:

  select unix_timestamp("2001/3/26") - unix_timestamp("2001/3/25");

Is it possible that you copied this bug from the MySQL code?

Anyway, this could start causing big problems in date related software next year (or maybe nobody would notice)...

My configure line (I don't see how php.ini could be relevant):

./configure --with-apxs=/usr/sbin/apxs --with-xml --with-pdflib --with-zlib --with-mysql=/usr --with-oracle --with-ldap

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Full Bug description available at: http://bugs.php.net/?id=6781 

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