- date_diff: documentation ( source)
- date_default_timezone_set: documentation ( source)
<?php
date_default_timezone_set('Europe/Berlin');
$date1 = new DateTime("2015-03-29 02:00:00", new DateTimeZone('Europe/Berlin'));
$date2 = new DateTime("2015-03-29 03:00:00", new DateTimeZone('UTC'));
$interval = date_diff($date1, $date2);
echo $interval->format('%H Hour(s) %I Minute(s) %S Second(s)' );
?>