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Date: Fri, 13 Feb 2015 13:03:40 +0900
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To: "internals@lists.php.net" <internals@lists.php.net>, Derick Rethans <derick@php.net>
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Subject: Legal date generated from illegal date
From: yohgaki@ohgaki.net (Yasuo Ohgaki)

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Hi Derick,

I came across with strange DataTime generates legal date from illegal date.
http://3v4l.org/rKFIg

<?php
$date = new DateTime('0000-00-00');
var_dump($date->format('Y-m-d H:i:s'));
$date = new DateTime('0000-01-00');
var_dump($date->format('Y-m-d H:i:s'));
$date = new DateTime('0000-00-01'); // "-0001-12-01 00:00:00" legal date
from illegal date
var_dump($date->format('Y-m-d H:i:s'));
$date = new DateTime('0000-01-01');
var_dump($date->format('Y-m-d H:i:s'));

$date = new DateTime('0001-00-00');
var_dump($date->format('Y-m-d H:i:s')); // "-0002-11-30 00:00:00" legal
date from illegal
$date = new DateTime('0001-01-00');
var_dump($date->format('Y-m-d H:i:s')); // "-0002-12-31 00:00:00" legal
date from illegal
$date = new DateTime('0001-00-01');
var_dump($date->format('Y-m-d H:i:s')); // "-0002-12-01 00:00:00" legal
date from illegal

$date = new DateTime('-0001-00-00');
var_dump($date->format('Y-m-d H:i:s')); // "-0002-11-30 00:00:00" legal
date from illegal
$date = new DateTime('-0001-01-00');
var_dump($date->format('Y-m-d H:i:s')); // "-0002-12-31 00:00:00" legal
date from illegal
$date = new DateTime('-0001-00-01');
var_dump($date->format('Y-m-d H:i:s')); // "-0002-12-01 00:00:00" legal
date from illegal


$date = new DateTime('0001-01-01'); // Correct date
var_dump($date->format('Y-m-d H:i:s'));
$date = new DateTime('-0001-01-01'); // Correct date
var_dump($date->format('Y-m-d H:i:s'));
?>

DateTime raises exceptions like month 13 or day 32, but not for some
illegal dates.

It seems this behavior is fixed/changed in 5.2.4 partially.
I was about to report this behavior as a bug, but I thought it may be
better to ask here
the reason why it behaves like this.

Is there reason that some illegal dates are allowed and result in strange
date?

One reason I can think of is MySQL. MySQL converts illegal date to
0000-00-00.
All the above script's output is out of MySQL DateTime/TimeStamp range, so
they
are converted 0000-00-00 under MySQL.

Even if PHP DateTime supports 0000-00-00 as invalid date, why don't make it
return
0000-00-00 when input is 0000-00-00?

Since these illegal dates are rather obvious, I thought there might be some
reasons behind.

ext/date/tests/bug41523-64bit.phpt
ext/date/tests/bug41523.phpt

These 2 tests use 0000-00-00 and expects the strange date.

ext/date/tests/bug62852_var3.phpt

This test unseliaizes 0000-00-00 date and raises exception.

I see controversial behavior here, unserialize raises error while new
DateTime('0000-00-00') doesn't.

If it's a bug, I'll just file it as a bug.

Thank you.

Regards,

--
Yasuo Ohgaki
yohgaki@ohgaki.net

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