Bug #52480 [Asn->Csd]: Incorrect difference using DateInterval

Edit report at https://bugs.php.net/bug.php?id=52480&edit=1 ID: 52480 Updated by: heiglandreas@php.net Reported by: alex dot joyce at staff dot comcen dot com dot au Summary: Incorrect difference using DateInterval -Status: Assigned +Status: Closed Type: Bug Package: Date/time related Operating System: Debian 5.0.3 PHP Version: 5.3.3 Assigned To: derick Block user comment: N Private report: N New Comment: This seems to be fixed in supported versions of PHP. Therefore I'm closing this issue. php > $date_start = new DateTime('2010-03-01'); php > $date_end = new DateTime('2010-07-29'); php > php > $interval = $date_start->diff($date_end); php > php > print_r($interval); DateInterval Object ( [y] => 0 [m] => 4 [d] => 28 [h] => 0 [i] => 0 [s] => 0 [f] => 0 [weekday] => 0 [weekday_behavior] => 0 [first_last_day_of] => 0 [invert] => 0 [days] => 150 [special_type] => 0 [special_amount] => 0 [have_weekday_relative] => 0 [have_special_relative] => 0 ) Previous Comments: ------------------------------------------------------------------------ [2016-11-23 07:14:51] lebeker at gmail dot com Still got a problems: (new DateTime('2016-10-01'))->diff((new DateTime('2016-10-31'))) // 1 month (new DateTime('2016-11-01'))->diff((new DateTime('2016-11-30'))) // 29 days either first should be 30 days, or the second one 1 month (new DateTime('2016-11-01'))->diff((new DateTime('2016-12-01'))) // 30 days but that's definitely 1 whole month and what's more interesting (new DateTime('2016-11-01'))->diff((new DateTime('2016-11-31'))) // 30 days but there is no such date as '2016-11-31', but that's probably another bug. PHP 7.0.8-0ubuntu0.16.04.3 ------------------------------------------------------------------------ [2016-02-12 01:56:26] pinballfan at outlook dot com After trying Marcel's code I got the same 'problem' on PHP 5.6 on a 64bit Windows 10 machine. However unexpected the result, I believe it is consistent with how PHP's datetime rounds dates around. Using this example: $date1 = new DateTime('2011-08-31T00:00:00Z'); $date2 = new DateTime('2012-03-01T00:00:00Z'); $interval = $date1->diff($date2); var_dump($interval); $interval->m = 5 $interval->d = 30 The expectation might be 6 months and 1 day What I'm guessing might be happening is that PHP starts adding 1 month like so: 2011-08-31 = starting date 2011-09-31 = starting date + 1 month (but there is no such thing as sept 31!) 2011-10-01 = date now wraps around to 2011-10-01 since 2011-09-31 doesn't exist 2011-11-01 = + 1 month (2 total) 2011-12-01 = + 1 month (3 total) 2012-01-01 = + 1 month (4 total) 2012-02-01 = + 1 month (5 total) 2012-03-01 = When diff'ing PHP does NOT include the final date maybe like DatePeriod. So that could be how it arrived at 5m and 30d ------------------------------------------------------------------------ [2015-01-12 09:43:52] marcel at berteler dot co dot za I experience the same issue where the month is incorrectly calculated: $Dob = new DateTime(); $Dob->setDate(2011, 8, 31); $Dob->setTime(0,0,0); $VisitDate = new DateTime(); $VisitDate->setDate(2012, 03, 01); $VisitDate->setTime(0,0,0); $interval = $Dob->diff($VisitDate); echo $interval->m; echo $interval->d; Should return 6 & 1 but returns 5 & 30. Changing the timezones still returns unexpected results: $Dob = new DateTime(); $Dob->setTimezone(new DateTimeZone('UTC')); $Dob->setDate(2011, 8, 30); $Dob->setTime(0,0,0); $VisitDate = new DateTime(); $VisitDate->setTimezone(new DateTimeZone('UTC')); $VisitDate->setDate(2012, 2, 1); $VisitDate->setTime(0,0,0); $interval = $Dob->diff($VisitDate); echo $interval->m; (returns 5) echo $interval->d; (return 2) 2011-08-30 to 2012-03-01 return 6 months and 0 days. Tried it in on both a Linux and Windows server and same result. ------------------------------------------------------------------------ [2014-11-19 10:00:52] ilantipov at gmail dot com Had the same issue diff between 01-04-2014 and 01-07-2014 : DateTime Object ( [date] => 2014-04-01 00:00:00.000000 [timezone_type] => 3 [timezone] => Europe/Moscow ) DateTime Object ( [date] => 2014-07-01 00:00:00.000000 [timezone_type] => 3 [timezone] => Europe/Moscow ) DateInterval Object ( [y] => 0 [m] => 2 [d] => 30 [h] => 0 [i] => 0 [s] => 0 [weekday] => 0 [weekday_behavior] => 0 [first_last_day_of] => 0 [invert] => 1 [days] => 91 [special_type] => 0 [special_amount] => 0 [have_weekday_relative] => 0 [have_special_relative] => 0 ) The right interval is 3 month. Not 2 month 30 days. Both dates have same timezone. If I add date_default_timezone_set('UTC') before diff - everything works fine; ------------------------------------------------------------------------ [2014-01-25 19:24:54] kulakov74 at yandex dot ru I stumbled upon this seemingly wrong behaviour too, while studying the manual, and was all about to add a confirming comment but finally realized the reason behind it. The explanation is that the diff() method first converts its operands to UTC. In cases when the converion changes their months the number of days in the month may change too. For ex. 2010-03-01/2010-07-29 in the very 1st example, when in Europe/Copenhagen, actually converts to 2010-02-28 23:00:00/2010-07-28 23:00:00, hence the difference 5 months 0 days. The conversion explains why the number of hours in the time part matters and should be equal or greater than the timezone offset from UTC in order to avoid the effect. Another consequence of the UTC conversion is that the function does not respect any DST shifts (it that matters for you). Using strtotime() for the same dates and subtracting the timestamps might yield a different result (+/-1 hour) if a DST switch is within the dates period. I also recommend using a DateTimeZone object for DateTime instead of changing the global TZ for all date functions: $oTZ=new DateTimeZone('Europe/Moscow'); $DT1=new DateTime('2010-03-01', $oTZ); ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at https://bugs.php.net/bug.php?id=52480 -- Edit this bug report at https://bugs.php.net/bug.php?id=52480&edit=1