Description:
------------
How to reproduce: create a DateTime object $dateTime with value of year 2015 (haven't tested other years), set any Russian timezone (e.g. Europe/Moscow), check the result of $dateTime->format('H:i') and compare with result of IntlDateFormatter::format with the same timezone. 
Problem exists in versions 5.6.20+dfsg-0+deb8u1 (debian jessie), 5.4.45 (CentOS) and 7.0.4 (Ubuntu). There was a similar bug (68434), marked as closed with a comment stating that "the data at least should be updated in the next release." Well, it certainly should, since 2014.

Test script:
---------------
$now = new \DateTime();
$russian = new\DateTimeZone('Europe/Moscow');
$now->setTimezone($russian);
$fmt = new IntlDateFormatter(
 'en-US',
 IntlDateFormatter::FULL,
 IntlDateFormatter::FULL,
 'Europe/Moscow',
 IntlDateFormatter::GREGORIAN
 );
echo $now->format('Y-m-d H:i:s');
echo $fmt->format($now);

Expected result:
----------------
2016-05-17 21:26:38
Tuesday, May 17, 2016 at 09:26:38 PM Moscow Standard Time


Actual result:
--------------
2016-05-17 21:26:38
Tuesday, May 17, 2016 at 10:26:38 PM Moscow Standard Time