#20382 [Com]: strtotime ("Monday", $date) can produce incorrect output

[pierre dot baudracco at aliacom dot fr]

ID: 20382
Comment by: pierre dot baudracco at aliacom dot fr
Reported By: nickj-phpbugs at nickj dot org
Status: Verified
Bug Type: Date/time related
Operating System: All
PHP Version: 4.3.0-dev
New Comment:

This bug is reappearing this week from monday 2003-10-20.
Which is a week having a daylight saving transition (this week-end).


Previous Comments:
------------------------------------------------------------------------

[2003-04-06 18:47:03] scottmacvicar at ntlworld dot com

This is a DST problem by the looks of it. The specific dates mentioned
are when DST takes effect which is the last sunday in March.

------------------------------------------------------------------------

[2002-11-12 19:46:28] nickj-phpbugs at nickj dot org

OK, I decided that was needed was some kind of automated testing, so I
wrote it:
============================================
#!/root/php4-200211122230 -q
<?php

// report any errors at all
error_reporting (E_ALL);

// pass a date, supply a strtotime modifier, and get a date back
function getDateWithModifier($date, $modifier) {
list ($year, $month, $day) = explode ("-",$date);
$starting_timestamp = mktime (1,1,1,$month,$day,$year);
$timestamp_with_modifier = strtotime ($modifier,
$starting_timestamp);
return date("Y-n-j", $timestamp_with_modifier);
}

/*
** @desc: for the specified date, will find the date for the desired
day of the
** week that is also in the same week. Does NOT use 'strtotime'
*/
function getDayOfTheWeekFromDate($date, $desired_day_of_week) {
// weekdays - note special case for sundays (7, not 0), so as to treat
as end of week, not start
$weekdays = array ("Sunday" => 7, "Monday" => 1, "Tuesday" => 2,
"Wednesday" => 3,
"Thursday" => 4, "Friday" => 5, "Saturday"
=> 6);

// convert into a number
$desired_day_of_week_number = $weekdays[$desired_day_of_week];

// see what day we have currently
list ($year, $month, $day) = explode ("-",$date);
$date_day_of_week = date("w", mktime
(17,17,17,$month,$day,$year));

$new_day = $day+(($desired_day_of_week_number-$date_day_of_week)+7) %
7;
return date("Y-n-j", mktime (17,17,17,$month,$new_day,$year));
}


// run an automated test to compare the output of these two functions,
and complain if they differ
for ($i=1; $i<1000; $i++) {
$date = date("Y-n-j", mktime (17,17,17,1,$i,1999));
$strtotime_date = getDateWithModifier($date, "Monday");
$other_date = getDayOfTheWeekFromDate($date, "Monday");
if ($strtotime_date != $other_date) {
print "Discrepancy for $date - results were $strtotime_date vs
$other_date\n";
}
}

print "PHP version: " . phpversion(). "<br>\n";

?>
============================================


Here's the output that I get:
============================================
[root@www tmp]# ./automated-date-test.php
Discrepancy for 1999-3-23 - results were 1999-3-28 vs 1999-3-29
Discrepancy for 1999-3-24 - results were 1999-3-28 vs 1999-3-29
Discrepancy for 1999-3-25 - results were 1999-3-28 vs 1999-3-29
Discrepancy for 1999-3-26 - results were 1999-3-28 vs 1999-3-29
Discrepancy for 1999-3-27 - results were 1999-3-28 vs 1999-3-29
Discrepancy for 1999-3-28 - results were 1999-3-28 vs 1999-3-29
Discrepancy for 2000-3-21 - results were 2000-3-26 vs 2000-3-27
Discrepancy for 2000-3-22 - results were 2000-3-26 vs 2000-3-27
Discrepancy for 2000-3-23 - results were 2000-3-26 vs 2000-3-27
Discrepancy for 2000-3-24 - results were 2000-3-26 vs 2000-3-27
Discrepancy for 2000-3-25 - results were 2000-3-26 vs 2000-3-27
Discrepancy for 2000-3-26 - results were 2000-3-26 vs 2000-3-27
Discrepancy for 2001-3-20 - results were 2001-3-25 vs 2001-3-26
Discrepancy for 2001-3-21 - results were 2001-3-25 vs 2001-3-26
Discrepancy for 2001-3-22 - results were 2001-3-25 vs 2001-3-26
Discrepancy for 2001-3-23 - results were 2001-3-25 vs 2001-3-26
Discrepancy for 2001-3-24 - results were 2001-3-25 vs 2001-3-26
Discrepancy for 2001-3-25 - results were 2001-3-25 vs 2001-3-26
PHP version: 4.3.0-dev<br>
[root@www tmp]#
============================================

In other words, the result for these 6 days of the year consistently
appears to be wrong. (I suppose I should be glad that the very first
date I choose to test this function with just by fluke happened to be
one of those 6 days, as opposed to causing mysterious problems later!)


Does anyone else get any results that appear incorrect on running this
script?

------------------------------------------------------------------------

[2002-11-12 18:10:27] nickj-phpbugs at nickj dot org

Happy to comply. I tried it with the CVS snapshot (php4-200211122230),
output was:
================================================== ===========
[root@www tmp]# ./script.php
<hr>
from 2001-3-17, goto monday: 2001-3-19; should be 2001-3-19.<br>
from 2001-3-18, goto monday: 2001-3-19; should be 2001-3-19.<br>
from 2001-3-19, goto monday: 2001-3-19; should be 2001-3-19.<br>
from 2001-3-20, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-21, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-22, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-23, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-24, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-25, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-26, goto monday: 2001-3-26; should be 2001-3-26.<br>
from 2001-3-27, goto monday: 2001-4-2 ; should be 2001-4-2.<br>
<hr>
PHP version: 4.3.0-dev<br>
[root@www tmp]#
================================================== ===========

i.e. same problem. The location of the php command-line executable
appears to have changed to 'sapi/cli/php' (in the PHP 4.2.3 build
process the executable just ends up in the root of the source
directory), so this was what I used, hope this is OK.

Here is some more info related to the problem that may or may not be
relevant:

* This machine and I are located in Sydney, Australia. The machine's
timezone as shown in 'timeconfig' is set of "Australia/Sydney", and
"Hardware clock set to GMT" is shown turned off. Output of the 'date'
command looks like this: "Wed Nov 13 10:40:22 EST 2002". Sydney is
(depending on daylight savings) around GMT + 10 hours.

* I've found today that there was a daylight savings transition for
this timezone in that week. From:
[url]http://www.dstc.qut.edu.au/DST/marg/daylight.html[/url] - "[Daylight savings]
ends at 3am on Sunday 25 March 2001. Clocks should be turned back one
hour to read 2am (Australian Eastern Standard Time)."

* Since there was a daylight savings transition, I've now tried various
parameters to the 'mktime' line, in case the hour/minute/second
parameters chosen were causing problems because they were too close to
the time transition. I've tried the following parameters, all of which
produce the same incorrect result:
- mktime (23,23,23,$month,$day,$year);
- mktime (15,15,15,$month,$day,$year);
- mktime (10,10,10,$month,$day,$year);
- mktime (5,5,5,$month,$day,$year);
- mktime (1,1,1,$month,$day,$year);

------------------------------------------------------------------------

[2002-11-12 06:17:41] [email]sniper@php.net[/email]

Please try using this CVS snapshot:

[url]http://snaps.php.net/php4-latest.tar.gz[/url]

For Windows:

[url]http://snaps.php.net/win32/php4-win32-latest.zip[/url]


Your script produces the expected dates for me with latest CVS
snapshot. Please give try it out.


------------------------------------------------------------------------

[2002-11-12 02:11:16] nickj-phpbugs at nickj dot org

Strtotime() appears to produce incorrect output under some
circumstances - specifically when wanting the date of a particular day
of the week day of the week from a given starting date. For example,
using 2001-3-20 as a starting point, we want the date for the next
Monday. The correct answer is the 26th, but the result produced is the
25th (a Sunday). The correct result is given sometimes, so this appears
to depend on the input.

A sample script to illustrate:
================================================== =====
#!/root/php-4.2.3 -q
<?php

// report any errors at all
error_reporting (E_ALL);

// pass a date, supply a strtotime modifier, and get a date back
function getDateWithModifier($date, $modifier) {
list ($year, $month, $day) = explode ("-",$date);
$starting_timestamp = mktime (10,10,10,$month,$day,$year);
$timestamp_with_modifier = strtotime ($modifier,
$starting_timestamp);
return date("Y-n-j", $timestamp_with_modifier);
}

print "<hr>\n";
print "from 2001-3-17, goto monday: " .
getDateWithModifier("2001-3-17", "Monday") . "; should be
2001-3-19.<br>\n";
print "from 2001-3-18, goto monday: " .
getDateWithModifier("2001-3-18", "Monday") . "; should be
2001-3-19.<br>\n";
print "from 2001-3-19, goto monday: " .
getDateWithModifier("2001-3-19", "Monday") . "; should be
2001-3-19.<br>\n";
print "from 2001-3-20, goto monday: " .
getDateWithModifier("2001-3-20", "Monday") . "; should be 2001-3-26
###.<br>\n";
print "from 2001-3-21, goto monday: " .
getDateWithModifier("2001-3-21", "Monday") . "; should be 2001-3-26
###.<br>\n";
print "from 2001-3-22, goto monday: " .
getDateWithModifier("2001-3-22", "Monday") . "; should be 2001-3-26
###.<br>\n";
print "from 2001-3-23, goto monday: " .
getDateWithModifier("2001-3-23", "Monday") . "; should be 2001-3-26
###.<br>\n";
print "from 2001-3-24, goto monday: " .
getDateWithModifier("2001-3-24", "Monday") . "; should be 2001-3-26
###.<br>\n";
print "from 2001-3-25, goto monday: " .
getDateWithModifier("2001-3-25", "Monday") . "; should be 2001-3-26
###.<br>\n";
print "from 2001-3-26, goto monday: " .
getDateWithModifier("2001-3-26", "Monday") . "; should be
2001-3-26.<br>\n";
print "from 2001-3-27, goto monday: " .
getDateWithModifier("2001-3-27", "Monday") . " ; should be
2001-4-2.<br>\n";
print "<hr>\n";

print "PHP version: " . phpversion(). "<br>\n";

?>
================================================== =====

Produces this output:
================================================== =====
[root@www tmp]# ./script.php
<hr>
from 2001-3-17, goto monday: 2001-3-19; should be 2001-3-19.<br>
from 2001-3-18, goto monday: 2001-3-19; should be 2001-3-19.<br>
from 2001-3-19, goto monday: 2001-3-19; should be 2001-3-19.<br>
from 2001-3-20, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-21, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-22, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-23, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-24, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-25, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-26, goto monday: 2001-3-26; should be 2001-3-26.<br>
from 2001-3-27, goto monday: 2001-4-2 ; should be 2001-4-2.<br>
<hr>
PHP version: 4.2.3<br>
[root@www tmp]#
================================================== ======

Expected output: The 6 lines with "###" are expected to produce the
indicated output, but do not.

Problem was noticed today in PHP 4.06, and then verified as being
reproducible in PHP 4.2.3 (same output).

PHP 4.2.3 configured with:
../configure --with-mysql --enable-xml --enable-wddx


------------------------------------------------------------------------


--
Edit this bug report at [url]http://bugs.php.net/?id=20382&edit=1[/url]

[Robert at steelrat dot homeip dot net]

ID: 20382
Comment by: Robert at steelrat dot homeip dot net
Reported By: nickj-phpbugs at nickj dot org
Status: Verified
Bug Type: Date/time related
Operating System: All
PHP Version: 4.3.0-dev
New Comment:

I can confirm that the above problem has re-occured for me! I'm using
Windows Server 2003 and latest rc of PHP. My code is simple:

$today = strtotime("today GMT");
echo "Next Friday is ".date( "l, j F, Y", strtotime("first Friday",
$today))."!<p>\n";
print "PHP version: " . phpversion(). "<br>\n";

and the result:

Next Friday is Thursday, 30 October, 2003!

PHP version: 4.3.4RC2

I use this function on one of my pages and I've only just seen this
appear. Worked perfectly until today!


Previous Comments:
------------------------------------------------------------------------

[2003-10-21 06:37:52] pierre dot baudracco at aliacom dot fr

This bug is reappearing this week from monday 2003-10-20.
Which is a week having a daylight saving transition (this week-end).

------------------------------------------------------------------------

[2003-04-06 18:47:03] scottmacvicar at ntlworld dot com

This is a DST problem by the looks of it. The specific dates mentioned
are when DST takes effect which is the last sunday in March.

------------------------------------------------------------------------

[2002-11-12 19:46:28] nickj-phpbugs at nickj dot org

OK, I decided that was needed was some kind of automated testing, so I
wrote it:
============================================
#!/root/php4-200211122230 -q
<?php

// report any errors at all
error_reporting (E_ALL);

// pass a date, supply a strtotime modifier, and get a date back
function getDateWithModifier($date, $modifier) {
list ($year, $month, $day) = explode ("-",$date);
$starting_timestamp = mktime (1,1,1,$month,$day,$year);
$timestamp_with_modifier = strtotime ($modifier,
$starting_timestamp);
return date("Y-n-j", $timestamp_with_modifier);
}

/*
** @desc: for the specified date, will find the date for the desired
day of the
** week that is also in the same week. Does NOT use 'strtotime'
*/
function getDayOfTheWeekFromDate($date, $desired_day_of_week) {
// weekdays - note special case for sundays (7, not 0), so as to treat
as end of week, not start
$weekdays = array ("Sunday" => 7, "Monday" => 1, "Tuesday" => 2,
"Wednesday" => 3,
"Thursday" => 4, "Friday" => 5, "Saturday"
=> 6);

// convert into a number
$desired_day_of_week_number = $weekdays[$desired_day_of_week];

// see what day we have currently
list ($year, $month, $day) = explode ("-",$date);
$date_day_of_week = date("w", mktime
(17,17,17,$month,$day,$year));

$new_day = $day+(($desired_day_of_week_number-$date_day_of_week)+7) %
7;
return date("Y-n-j", mktime (17,17,17,$month,$new_day,$year));
}


// run an automated test to compare the output of these two functions,
and complain if they differ
for ($i=1; $i<1000; $i++) {
$date = date("Y-n-j", mktime (17,17,17,1,$i,1999));
$strtotime_date = getDateWithModifier($date, "Monday");
$other_date = getDayOfTheWeekFromDate($date, "Monday");
if ($strtotime_date != $other_date) {
print "Discrepancy for $date - results were $strtotime_date vs
$other_date\n";
}
}

print "PHP version: " . phpversion(). "<br>\n";

?>
============================================


Here's the output that I get:
============================================
[root@www tmp]# ./automated-date-test.php
Discrepancy for 1999-3-23 - results were 1999-3-28 vs 1999-3-29
Discrepancy for 1999-3-24 - results were 1999-3-28 vs 1999-3-29
Discrepancy for 1999-3-25 - results were 1999-3-28 vs 1999-3-29
Discrepancy for 1999-3-26 - results were 1999-3-28 vs 1999-3-29
Discrepancy for 1999-3-27 - results were 1999-3-28 vs 1999-3-29
Discrepancy for 1999-3-28 - results were 1999-3-28 vs 1999-3-29
Discrepancy for 2000-3-21 - results were 2000-3-26 vs 2000-3-27
Discrepancy for 2000-3-22 - results were 2000-3-26 vs 2000-3-27
Discrepancy for 2000-3-23 - results were 2000-3-26 vs 2000-3-27
Discrepancy for 2000-3-24 - results were 2000-3-26 vs 2000-3-27
Discrepancy for 2000-3-25 - results were 2000-3-26 vs 2000-3-27
Discrepancy for 2000-3-26 - results were 2000-3-26 vs 2000-3-27
Discrepancy for 2001-3-20 - results were 2001-3-25 vs 2001-3-26
Discrepancy for 2001-3-21 - results were 2001-3-25 vs 2001-3-26
Discrepancy for 2001-3-22 - results were 2001-3-25 vs 2001-3-26
Discrepancy for 2001-3-23 - results were 2001-3-25 vs 2001-3-26
Discrepancy for 2001-3-24 - results were 2001-3-25 vs 2001-3-26
Discrepancy for 2001-3-25 - results were 2001-3-25 vs 2001-3-26
PHP version: 4.3.0-dev<br>
[root@www tmp]#
============================================

In other words, the result for these 6 days of the year consistently
appears to be wrong. (I suppose I should be glad that the very first
date I choose to test this function with just by fluke happened to be
one of those 6 days, as opposed to causing mysterious problems later!)


Does anyone else get any results that appear incorrect on running this
script?

------------------------------------------------------------------------

[2002-11-12 02:11:16] nickj-phpbugs at nickj dot org

Strtotime() appears to produce incorrect output under some
circumstances - specifically when wanting the date of a particular day
of the week day of the week from a given starting date. For example,
using 2001-3-20 as a starting point, we want the date for the next
Monday. The correct answer is the 26th, but the result produced is the
25th (a Sunday). The correct result is given sometimes, so this appears
to depend on the input.

A sample script to illustrate:
================================================== =====
#!/root/php-4.2.3 -q
<?php

// report any errors at all
error_reporting (E_ALL);

// pass a date, supply a strtotime modifier, and get a date back
function getDateWithModifier($date, $modifier) {
list ($year, $month, $day) = explode ("-",$date);
$starting_timestamp = mktime (10,10,10,$month,$day,$year);
$timestamp_with_modifier = strtotime ($modifier,
$starting_timestamp);
return date("Y-n-j", $timestamp_with_modifier);
}

print "<hr>\n";
print "from 2001-3-17, goto monday: " .
getDateWithModifier("2001-3-17", "Monday") . "; should be
2001-3-19.<br>\n";
print "from 2001-3-18, goto monday: " .
getDateWithModifier("2001-3-18", "Monday") . "; should be
2001-3-19.<br>\n";
print "from 2001-3-19, goto monday: " .
getDateWithModifier("2001-3-19", "Monday") . "; should be
2001-3-19.<br>\n";
print "from 2001-3-20, goto monday: " .
getDateWithModifier("2001-3-20", "Monday") . "; should be 2001-3-26
###.<br>\n";
print "from 2001-3-21, goto monday: " .
getDateWithModifier("2001-3-21", "Monday") . "; should be 2001-3-26
###.<br>\n";
print "from 2001-3-22, goto monday: " .
getDateWithModifier("2001-3-22", "Monday") . "; should be 2001-3-26
###.<br>\n";
print "from 2001-3-23, goto monday: " .
getDateWithModifier("2001-3-23", "Monday") . "; should be 2001-3-26
###.<br>\n";
print "from 2001-3-24, goto monday: " .
getDateWithModifier("2001-3-24", "Monday") . "; should be 2001-3-26
###.<br>\n";
print "from 2001-3-25, goto monday: " .
getDateWithModifier("2001-3-25", "Monday") . "; should be 2001-3-26
###.<br>\n";
print "from 2001-3-26, goto monday: " .
getDateWithModifier("2001-3-26", "Monday") . "; should be
2001-3-26.<br>\n";
print "from 2001-3-27, goto monday: " .
getDateWithModifier("2001-3-27", "Monday") . " ; should be
2001-4-2.<br>\n";
print "<hr>\n";

print "PHP version: " . phpversion(). "<br>\n";

?>
================================================== =====

Produces this output:
================================================== =====
[root@www tmp]# ./script.php
<hr>
from 2001-3-17, goto monday: 2001-3-19; should be 2001-3-19.<br>
from 2001-3-18, goto monday: 2001-3-19; should be 2001-3-19.<br>
from 2001-3-19, goto monday: 2001-3-19; should be 2001-3-19.<br>
from 2001-3-20, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-21, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-22, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-23, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-24, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-25, goto monday: 2001-3-25; should be 2001-3-26 ###.<br>
from 2001-3-26, goto monday: 2001-3-26; should be 2001-3-26.<br>
from 2001-3-27, goto monday: 2001-4-2 ; should be 2001-4-2.<br>
<hr>
PHP version: 4.2.3<br>
[root@www tmp]#
================================================== ======

Expected output: The 6 lines with "###" are expected to produce the
indicated output, but do not.

Problem was noticed today in PHP 4.06, and then verified as being
reproducible in PHP 4.2.3 (same output).

PHP 4.2.3 configured with:
../configure --with-mysql --enable-xml --enable-wddx


------------------------------------------------------------------------


--
Edit this bug report at [url]http://bugs.php.net/?id=20382&edit=1[/url]