Edit report at https://bugs.php.net/bug.php?id=65608&edit=1
ID: 65608 Comment by: anon at anon dot anon Reported by: jiri dot kapinus at gmail dot com Summary: Possible problems with the UNIX timestamp Status: Not a bug Type: Feature/Change Request Package: Date/time related PHP Version: Irrelevant Block user comment: N Private report: N New Comment: The "bug" emerges from the assumption that if you take a time in time zone A, offset it by some amount, and then convert it to time zone B; you would get the same result as converting it to time zone B first, and then offsetting it. Unfortunately, that assumption isn't true. Monticello used to be on Central Time. Now it's on Eastern Time. It's definitely annoying, but it's not a bug in PHP. Time is HARD. For more pitfalls, see: * http://infiniteundo.com/post/25326999628/falsehoods-programmers-believe-about-time * http://infiniteundo.com/post/25509354022/more-falsehoods-programmers-believe-about-time-wisdom Previous Comments: ------------------------------------------------------------------------ [2013-09-04 02:47:48] ras...@php.net I don't understand what you think the bug is here. Of course you can't just add the timestamp to the starting date for Unix time and expect it to work for all timezones. It completely ignores daylight savings along the way. If you can explain yourself better using a single timezone and prove that what you are seeing isn't simply the effect of daylight savings you can re-open this. ------------------------------------------------------------------------ [2013-09-03 08:45:59] jiri dot kapinus at gmail dot com instead of ,,when convert this time to America/Kentucky/Monticello, it returns following date for Monticello timezone" is right this: ,,when we set the time with parametr UNIX timestamp 0, it returns UNIX timestamp start time for Monticello timezone" ------------------------------------------------------------------------ [2013-09-03 08:28:49] jiri dot kapinus at gmail dot com Description: ------------ The UNIX timestamp gives the number of seconds since January 1 1970 00:00:00 UTC. But value of UNIX timestamp can be different, that in really is. More information on http://www.najdouvas.cz/unix-timestamp-error/ Test script: --------------- <?php date_default_timezone_set('UTC'); echo "Current time and date in UTC timezone: " . date("M d Y H:i:s", time()) . "<br>"; date_default_timezone_set('America/Kentucky/Monticello'); echo "Current time and date in America/Kentucky/Monticello timezone: " . date("M d Y H:i:s", time()) . "<br>"; echo "UNIX timestamp defined by Strtotime for now: " . strtotime("now") . " <br>"; $start = strtotime("now"); $zonestart = date("M d Y H:i:s", 00); echo "UNIX timestamp start at: Jan 01 1970 00:00:00 UTC<br>"; echo "when convert this time to America/Kentucky/Monticello, it returns following date for Monticello timezone<br>"; echo "UNIX timestamp start at: " . $zonestart . " America/Kentucky/Monticello timezone<br>"; echo "To this date we add UNIX timestamp for NOW time. The result may be the same as the current time and date for America/Kentucky/Monticello <br>"; $date = date_create($zonestart); $date->modify('+ ' . $start . ' sec'); echo "Result is: " . $date->format('M d Y H:i:s e') . "<br>"; date_default_timezone_set('UTC'); $date->setTimezone(new DateTimeZone("UTC")); echo "Changing this time to UTC timezone: " . $date->format('M d Y H:i:s e') . "<br><br>"; echo "When final date is not the same as the date at the begining, it means, that the UNIX timestamp don't give up exact number of second for this place or timezone. The UNIX timestamp gives the number of seconds since January 1 1970 00:00:00 UTC. But it's different for different places.<br><br>"; ?> ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=65608&edit=1
