Bug #62327 [Com]: Calculation error in DateTime::add() or DateTime::diff()

Edit report at https://bugs.php.net/bug.php?id=62327&edit=1 ID: 62327 Comment by: antonino dot spampinato86 at gmail dot com Reported by: helmut at qweb dot at Summary: Calculation error in DateTime::add() or DateTime::diff() Status: Open Type: Bug Package: Date/time related Operating System: Linux, Windows PHP Version: Irrelevant Block user comment: N Private report: N New Comment: Is the expected result, diff is likely to be unique for two dates. The php arithmetic is not one to one like the human one, in fact a month can be 30 days, 31, 28 or 29 if leap year. I show you the raw code, where I have voluntarily created and overwritten the variable $interval, if you try to comment on the second one will get an incorrect result but this is because the calculation is not one to one but as I explained above (diff is almost always unique ). https://3v4l.org/MKeKE This not a bug :) Previous Comments: ------------------------------------------------------------------------ [2017-07-09 13:54:12] xKhorasan+php at gmail dot com Submitted a pull request to derickr/timelib. https://github.com/derickr/timelib/pull/15 ------------------------------------------------------------------------ [2012-06-14 19:04:18] helmut at qweb dot at Description: ------------ The task was to shift a date-interval like [ begin: 2012-05-07, end: 2012-06-01 ] to another begin date like 2012-05-21 - an end date 2012-06-15 is expected (first example). The function shift_datetimeobject() uses DateTime::diff() and DateTime::add() to calculate the end date - it fails in the 3rd of 4 attempts. The second function shift_timestamp() uses timestamp to solve the same task. it works like expected. The bug was found on Windows Server 2008/Apache 2.4.2/PHP 5.4.4 and on Debian Linux squeeze/PHP 5.3.3-7+squeeze9 with Suhosin-Patch/cli and libapache2-mod-php5 5.3.3-7+squeeze9 Test script: --------------- function shift_datetimeobject($begin1, $end1, $begin2) { $dt_begin1 = new DateTime($begin1); $dt_end1 = new DateTime($end1); $span = $dt_begin1->diff($dt_end1); $dt_return = new DateTime($begin2); return array($dt_return->add($span), $span); } function shift_timestamp($begin1, $end1, $begin2) { $dt_begin1 = new DateTime($begin1); $st_begin1 = $dt_begin1->getTimestamp(); $dt_end1 = new DateTime($end1); $st_end1 = $dt_end1->getTimestamp(); $span = $st_end1 - $st_begin1; $dt_begin2 = new DateTime($begin2); $st_begin2 = $dt_begin2->getTimestamp(); $st_end2 = $st_begin2 + $span; $dt_end2 = new DateTime(); return $dt_end2->setTimestamp($st_end2); } $params = array( array('2012-05-07', '2012-06-01', '2012-05-21'), array('2012-06-11', '2012-07-13', '2012-06-18'), array('2012-06-25', '2012-07-27', '2012-07-02'), array('2012-07-09', '2012-07-27', '2012-07-16'), ); foreach ($params as $p) { $erg_object = shift_datetimeobject($p[0], $p[1], $p[2]); $erg_stamp = shift_timestamp($p[0], $p[1], $p[2]); printf("Params: %s, %s, %s\n", $p[0], $p[1], $p[2]); printf('$erg_stamp = %s' . "\n", $erg_stamp->format('Y-m-d')); printf('$erg_object[0] = %s' . "\n", $erg_object[0]->format('Y-m-d')); printf("span (object) = %s\n", $erg_object[1]->format('%a days %H:%I:%S')); if ($erg_object[0] == $erg_stamp) { echo "OK"; } else { echo "WRONG!"; } echo "\n\n"; } Expected result: ---------------- Params: 2012-05-07, 2012-06-01, 2012-05-21 Result: 2012-06-15 Params: 2012-06-11, 2012-07-13, 2012-06-18 Result: 2012-07-20 Params: 2012-06-25, 2012-07-27, 2012-07-02 Result: 2012-08-03 Params: 2012-07-09, 2012-07-27, 2012-07-16 Result: 2012-08-03 Actual result: -------------- Params: 2012-05-07, 2012-06-01, 2012-05-21 $erg_stamp = 2012-06-15 $erg_object[0] = 2012-06-15 span (object) = 25 days 00:00:00 OK Params: 2012-06-11, 2012-07-13, 2012-06-18 $erg_stamp = 2012-07-20 $erg_object[0] = 2012-07-20 span (object) = 32 days 00:00:00 OK Params: 2012-06-25, 2012-07-27, 2012-07-02 $erg_stamp = 2012-08-03 $erg_object[0] = 2012-08-04 span (object) = 32 days 00:00:00 WRONG! Params: 2012-07-09, 2012-07-27, 2012-07-16 $erg_stamp = 2012-08-03 $erg_object[0] = 2012-08-03 span (object) = 18 days 00:00:00 OK ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=62327&edit=1