Bug #6781 Updated: Error in mktime() funtion (Serious???)

ID: 6781 Updated by: s_esat@hotmail.com Reported By: landen@frg.eur.nl Status: Closed Bug Type: Date/time related Operating System: Linux RH 6.0, 6.1, 6.2 PHP Version: 4.0.1pl2 New Comment: I'm glad this hasn't been deleted! It's helped solved a problem due to DST. Thanks :) Previous Comments: ------------------------------------------------------------------------ [2000-09-17 04:33:46] derick@php.net You just discovered daylight savings time.... closing ------------------------------------------------------------------------ [2000-09-17 01:52:01] landen@frg.eur.nl 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 ;) ------------------------------------------------------------------------ [2000-09-17 00:56:01] landen@frg.eur.nl 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 seconds\n"; } } } 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 ------------------------------------------------------------------------ [2000-09-16 23:41:31] landen@frg.eur.nl 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 ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=6781&edit=1