Bug #76983 [Fbk]: date('i') returns wrong value for Dublin timezone

Edit report at https://bugs.php.net/bug.php?id=76983&edit=1 ID: 76983 Updated by: requinix@php.net Reported by: tomas at matrixinternet dot ie Summary: date('i') returns wrong value for Dublin timezone Status: Feedback Type: Bug Package: Date/time related Operating System: Ubuntu 16.04 PHP Version: 5.6.38 Block user comment: N Private report: N New Comment: The next question is whether you can reproduce with PHP 7.1, given that 5.6 and even 7.0 are no longer supported. And what are the precise version numbers of your tzdata on the AWS and non-AWS (presumably also 16.04) instances? Previous Comments: ------------------------------------------------------------------------ [2018-10-08 08:42:16] tomas at matrixinternet dot ie Yes, tzdata version on the affected system is 2018e. ------------------------------------------------------------------------ [2018-10-08 06:52:56] requinix@php.net It looks like tzdata had issues with the way it stored DST information for Europe/Dublin. What version of tzdata do you have installed? Is it at least 2018e? ------------------------------------------------------------------------ [2018-10-08 06:38:55] tomas at matrixinternet dot ie Description: ------------ We use date('I') (capital i) to detect daylight saving time being in action or not. It kept returning "1" quite happily throughout the summer. On 29/09/2018 around 7:00 am, it started returning "0", indicating a change to a winter time. This happened pretty much exactly one full month before the change was about to happen on October 29. Linux Timezone is: Europe/Dublin (IST, +0100) PHP timezone is set via date_default_timezone_set('Europe/Dublin'); date('I', strtotime('2018-09-29 02:00:00')) // returns "0" - which is wrong as DST is active now! date('I', strtotime('2018-11-29 02:00:00')) // returns "1" - which is wrong as DST is Summer time! This issue seems to happen specifically on Amazon AWS EC2 instances. A newly installed server instance returns the correct value for around a day, but then it seems to switch over. We weren't able to replicate this issue on a non-AWS instance. Test script: --------------- date_default_timezone_set('Europe/London'); if (date('I', strtotime('2018-09-29 02:00:00'))) { echo 'We are in DST!'; } else { echo 'We are not in DST!'; } date_default_timezone_set('Europe/Dublin'); if (date('I', strtotime('2018-09-29 02:00:00'))) { echo 'We are in DST!'; } else { echo 'We are not in DST!'; } date_default_timezone_set('Europe/Paris'); if (date('I', strtotime('2018-09-29 02:00:00'))) { echo 'We are in DST!'; } else { echo 'We are not in DST!'; } Expected result: ---------------- We are in DST! We are in DST! We are in DST! Actual result: -------------- We are in DST! We are not in DST! We are in DST! ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=76983&edit=1