- var_dump: documentation ( source)
- date_default_timezone_set: documentation ( source)
<?php
date_default_timezone_set("Europe/Vilnius");
$datetime1 = new DateTime('1970-01-01 11:55:00');
var_dump($datetime1->getOffset());
$datetime1 = new DateTime('2014-01-01 11:55:00');
var_dump($datetime1->getOffset());
?>