Zend_Date, ISO_8601, date parsing and local system clock - php

Question

I have a strange problem with Zend_Date object.
It seems that setters perform different operations with different system clock dates.
Let's assume that system date is 28 January 2013, following code:
$now=new Zend_Date(Zend_Date::ISO_8601);
$now->now();
echo '<br/>now: ' . $now->toString();
echo '<br/>now->day: ' . $now->get(Zend_Date::DAY);
echo '<br/>now->month: ' . $now->get(Zend_Date::MONTH);
echo '<br/>now->year: ' . $now->get(Zend_Date::YEAR);
$end=new Zend_Date('2013-02-25 14:23:34', Zend_Date::ISO_8601);
echo '<br/>end: ' . $end->toString();
$end->setHour('23')->setMinute('59')->setSecond('59')->setDay($now->get(Zend_Date::DAY))->setMonth($now->get(Zend_Date::MONTH))->setYear($now->get(Zend_Date::YEAR));
echo '<br/>endAfterSetters: ' . $end->toString();
will produce following output:
now: 28-01-2013 14:04:28
now->day: 28
now->month: 01
now->year: 2013
end: 25-02-2013 14:23:34
endAfterSetters: 28-01-2013 23:59:59
But if you change system clock to 29 January 2013, output is different from expectations:
now: 29-01-2013 14:07:22
now->day: 29
now->month: 01
now->year: 2013
end: 25-02-2013 14:23:34
endAfterSetters: 01-01-2013 23:59:59
Last output is 01-01-2013 23:59:59, but should be 29-01-2013 23:59:59 !
It happens on PHP 5.3.2 and 5.3.16, Zend_Framework 10.7, latest Zend_Date 24880 version.
Everyting worked fine in the past.
Any ideas why it happens?
P.S.: I have also found jquery datatime plugin malfunciton while using it at 29,30,31 January... But i will describe it in other question.

Answer 1

Remember that your setters are called in sequence. So when you call setDay(29) you're telling it to change the date to 29th February 2013, which isn't a valid date, so it's rolling that over to make it 1st March 2013. Then you call setMonth(1), which changes the month to January, giving you 1st January 2013.
You can control this behaviour by passing the extend_month option to the Zend_Date constructor, see: http://framework.zend.com/manual/1.12/en/zend.date.overview.html#zend.date.options.extendmonth