Bug->Doc #72470 [Opn]: modify() doesn't take into account DST changes

Edit report at https://bugs.php.net/bug.php?id=72470&edit=1 ID: 72470 Updated by: requinix@php.net Reported by: matthieux dot dekamen at gmail dot com Summary: modify() doesn't take into account DST changes Status: Open -Type: Bug +Type: Documentation Problem Package: Date/time related PHP Version: 7.1.0alpha1 Block user comment: N Private report: N New Comment: add() and modify() have different meanings. After all, two methods that did the same thing would be a bit odd. modify() will literally alter the date/time according to what you tell it. If you say "+23 hours" then it will add 23 to the "hour" value and adjust for overflow. 1000 + 23 hours = 3300 -> 0900 the next day. add() does what you are expecting: add an interval of time. It's generally the same thing, except during a DST transition the interval will be appear shorter or longer on the clock. 23 hours after 1000 = 0900 the next day - 1 hour "lost" due to the DST transition = 0800 the next day. Which gives me an idea for a bug report. Previous Comments: ------------------------------------------------------------------------ [2016-06-22 19:58:33] matthieux dot dekamen at gmail dot com Description: ------------ modify() doesn't take into account DST changes. For example, if I add 23 hours with DateInterval where a DST change occurs: echo date_default_timezone_get(); // prints Europe/Amsterdam $dateTime = new DateTime('2016-10-29 10:00:00'); $dateTime->add(new DateInterval('PT23H')); I get the expected result: 2016-10-30T08:00:00+01:00 (clock went backwards for 1 hour) But if I add 23 hours with the modify() function on the same date: $dateTime = new DateTime('2016-10-29 10:00:00'); $dateTime->modify('+ 23 hours'); I get: 2016-10-30T09:00:00+01:00 As you see the result here is different. modify() seems to not take into account DST changes. https://3v4l.org/4fncr ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=72470&edit=1