- date_default_timezone_set: documentation ( source)
<?php
date_default_timezone_set ( 'America/Chicago' );
$datetime_from_datetimestring = \DateTime::createFromFormat('Y-m-d H:i T', '2015-10-22 09:23 CDT');
echo $datetime_from_datetimestring->format('c');
echo PHP_EOL;
$datetime_from_iso8601 = new \DateTime('2015-10-22T08:50:39-0500','America/Chicago');
echo $datetime_from_iso8601->format('Y-m-d H:i T');