Fix DateObject->subMonth() bug related to non-UTC timezones

[kylehendricks]

$parts = $this->getDateParts($this->mktime($hour, $minute, $second, $date, $day, $year, false));

This purpose of this line is to help see if the day of month (ex: 30th, 31st) exists in the month we are adding/subtracting to. The problem with it is that mktime call is taking into account the timezone but the getDateParts is not. This will cause problems with times that are "ahead a month" of UTC. (Ex: a +4 timezone at 1 am on the first of a month). We first convert from local timezone to UTC with the mktime, getDateParts is then called which returns a UTC time. We need the resulting "overflow" time to be in the local timezone.

[froschdesign]

@kylehendricks
Thanks for the PR!

Please check the failure on Travis: https://travis-ci.org/zendframework/zf1/jobs/129276932#L498

[froschdesign]

@kylehendricks
I can not found a signed CLA.

[kylehendricks]

@froschdesign Can the CLA be e-signed?

[froschdesign]

@kylehendricks

Can the CLA be e-signed?

No. Print, fill, scan and email it.

[froschdesign]

@kylehendricks
Have you check the problems on Travis?

[kylehendricks]

Just sent the CLA, looking into the test failure now.

[kylehendricks]

@froschdesign I didn't notice all the tests in tests/Zend/DateTest.php so I moved my test into there.

I noticed that all the other Zend_Date add/sub month tests had a hidden dependency on the PHP default_timezone being set to the correct timezone that you are working with. My change should effectively eliminate that dependency.

[froschdesign]

@kylehendricks

so I moved my test into there.

Please create a new test method. Thanks!

[froschdesign]

@weierophinney
Can you look after the CLA? Thanks!