Description:
------------
IntlDateFormatter incorrectly adds a year to dates. One such date is provided in the test script.

Test script:
---------------
<?php

$timezone = new DateTimeZone('America/Chicago');
$formatter = new \IntlDateFormatter('en_US', null, null, $timezone, null, 'YYYY-MM-dd');
$date = new DateTime('2018-12-31', $timezone);
echo $formatter->format($date);

// expected: 2018-12-31
// actual:   2019-12-31

Expected result:
----------------
2018-12-31

Actual result:
--------------
2019-12-31