- strtotime: documentation ( source)
<?php
$date = new DateTime();
$date->setTimezone(new DateTimeZone('UTC'));
$date->setTimestamp(strtotime('2017-06-14 22:39:40'));
echo $date->format('F j, Y @ g:i:s a e');
$date->setTimestamp(strtotime('2017-06-14T19:39:38-07:00'));
echo $date->format('F j, Y @ g:i:s a e');