Bug #66453 [Nab]: Datetime modify bad result

Edit report at https://bugs.php.net/bug.php?id=66453&edit=1 ID: 66453 Updated by: requinix@php.net Reported by: mail at piotrantosik dot com Summary: Datetime modify bad result Status: Not a bug Type: Bug Package: *Calendar problems Operating System: Linux PHP Version: 5.5.7 Block user comment: N Private report: N New Comment: December 31st, 2013 most certainly does exist, and it does in every Gregorian calendar-based system around. That's not even up for discussion, it simply *is*. As for your question, read the documentation for date() [1] to see that "W" is the ISO 8601 week number [2], which is a two digit zero-padded number. [1] http://www.php.net/date [2] http://en.wikipedia.org/wiki/ISO_8601#Week_dates If you have questions, please ask on a mailing list or online forum to get more help. http://www.php.net/support.php Previous Comments: ------------------------------------------------------------------------ [2014-01-09 23:01:33] mail at piotrantosik dot com You're right, arithmetic is correct but 31-12-2013 is not exist in any calendars. Eg. i need display a week from this day: $d->format('W') return 01 - but maybe throw a exception? why return 01?? ------------------------------------------------------------------------ [2014-01-09 22:42:35] requinix@php.net Are you saying that December 31st is not a day? Because it totally is. The arithmetic is correct. ------------------------------------------------------------------------ [2014-01-09 22:35:25] mail at piotrantosik dot com Description: ------------ DateTime object return non exist day in calendar. Test script: --------------- $d = new \DateTime('2014-01-08'); $d->modify('-8 day'); Expected result: ---------------- echo $d->format('Y-m-d')) //2013-12-30 Actual result: -------------- echo $d->format('Y-m-d')) //2013-12-31 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=66453&edit=1