Description:
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DateTimeZone object doesn't calculate the offset correctly.

php > echo phpversion();
5.6.11
php > $timezone = new DateTimeZone('EEST');
php > $date = new DateTime('2015-07-16', new DateTimeZone('Europe/Bucharest'));
php > echo $date->format('T P');
EEST +03:00
php > $date->setTimezone($timezone);
php > echo $date->format('T P');
EEST +02:00

Test script:
---------------
<?php
$timezone = new DateTimeZone('EEST');
$date = new DateTime('2015-07-16', new DateTimeZone('Europe/Bucharest'));
$date->setTimezone($timezone);
echo $date->format('T P');

Expected result:
----------------
EEST +03:00

Actual result:
--------------
EEST +02:00