Bug #81458 [Csd]: Regression in PHP 8.1: Incorrect difference after timezone change

Edit report at https://bugs.php.net/bug.php?id=81458&edit=1 ID: 81458 Updated by: derick@php.net Reported by: kylekatarnls at gmail dot com Summary: Regression in PHP 8.1: Incorrect difference after timezone change Status: Closed Type: Bug Package: Date/time related PHP Version: 8.1Git-2021-09-18 (Git) Assigned To: derick Block user comment: N Private report: N New Comment: Should be fixed now Kyle, it had nothing to do with a regression, but with a missing "=" -> https://github.com/derickr/timelib/commit/b8885ede02dea903a42b82d1fcb99e708b76e384 Previous Comments: ------------------------------------------------------------------------ [2021-11-17 10:36:08] kylekatarnls at gmail dot com Hello derick, FYI I now get this returning me days = 0 using master branch, while if I properly understood your specs it should be 1: ``` date_default_timezone_set('UTC'); $a = new DateTime('2018-12-01 00:00'); $b = new DateTime('2018-12-02 00:01'); var_dump($a->diff($b)); ``` So it sounds now there is a regression when both are in UTC. ------------------------------------------------------------------------ [2021-11-08 09:40:54] git@php.net Automatic comment on behalf of derickr Revision: https://github.com/php/php-src/commit/904933e9185664148ce5459f93726f54f572b6c3 Log: Fixed bug #81458: Regression: Incorrect difference after timezone change ------------------------------------------------------------------------ [2021-11-05 12:46:17] derick@php.net FWIW, I started working on this, but it's a tad more work than I expected. ------------------------------------------------------------------------ [2021-11-02 21:00:33] kylekatarnls at gmail dot com Exactly absolute(floor(($one->unixTime - $two->unixTime) / 86400)) is a good fallback to calendar diff when ambiguous. Thank you. ------------------------------------------------------------------------ [2021-11-02 15:31:59] derick@php.net Kyle, would you agree to the following definition of what "days" should mean in this context? It was never really defined (https://www.php.net/manual/en/class.dateinterval.php#dateinterval.props.days) in the docs: - If the timezones are the same¹, use the values of year, month, and day to calculate "days" - If the timezones are not the same, use absolute(floor(($one->unixTime - $two->unixTime) / 86400)) ¹ A timezone is the same if both $one and $two are: - the same timezone type (1, 2, or 3) AND - if zonetype 1 (utc offset) or 2 (abbr), the UTC offsets are the same - if zonetype 3, the TZIDs (such as UTC / America/Toronto) are the same In your example, the timezone in $first and $second is not the same, as $first is zonetype 3 and has TZID "UTC", and $second is zonetype 3, but has the TZID "America/Toronto". If would then calculate absolute(floor((1530504000 - 1530417600) / 86400)) === 1. ------------------------------------------------------------------------ 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=81458 -- Edit this bug report at https://bugs.php.net/bug.php?id=81458&edit=1