out-1

chris@kinslayer:~/projects/phpbb/phpbb3 (develop-olympus) $ php -r 'date_default_timezone_set("Asia/Tokyo"); var_dump(gmdate("c"), date("c", gmdate("U") - date("Z")));'
string(25) "2011-09-24T23:31:48+00:00"
string(25) "2011-09-24T23:31:48+09:00"
chris@kinslayer:~/projects/phpbb/phpbb3 (develop-olympus) $ php -r 'date_default_timezone_set("Pacific/Auckland"); var_dump(gmdate("c"), date("c", gmdate("U") - date("Z")));'
string(25) "2011-09-24T23:31:59+00:00"
string(25) "2011-09-24T22:31:59+12:00"

out-2

1) phpbb_wrapper_gmgetdate_test::test_tz with data set #204 ('Antarctica/McMurdo')
--- Expected
+++ Actual
@@ @@
-2011-09-24 23:39:30
+2011-09-24 22:39:30


2) phpbb_wrapper_gmgetdate_test::test_tz with data set #207 ('Antarctica/South_Pole')
--- Expected
+++ Actual
@@ @@
-2011-09-24 23:39:30
+2011-09-24 22:39:30


3) phpbb_wrapper_gmgetdate_test::test_tz with data set #376 ('Pacific/Auckland')
--- Expected
+++ Actual
@@ @@
-2011-09-24 23:39:31
+2011-09-24 22:39:31


4) phpbb_wrapper_gmgetdate_test::test_tz with data set #377 ('Pacific/Chatham')
--- Expected
+++ Actual
@@ @@
-2011-09-24 23:39:31
+2011-09-24 22:39:31

test.php

<?php
	public function provider_tz()
	{
		$tzs = array_map(function($tz)
		{
			return array($tz);
		}, DateTimeZone::listIdentifiers());

		return $tzs;
	}

	/**
	 * @dataProvider provider_tz
	 */
	public function test_tz($timezone)
	{
		date_default_timezone_set($timezone);

		$this->assertSame(gmdate('Y-m-d H:i:s'), date("Y-m-d H:i:s", gmdate("U") - date("Z")));
	}