- var_dump: documentation ( source)
<?php
$dateUs = new \DateTimeImmutable('2015-10-20 00:00', new \DateTimeZone('America/New_York'));
$dateEu = new \DateTimeImmutable('2015-10-20 00:00', new \DateTimeZone('Europe/Prague'));
var_dump($dateUs->format('Y-m-d G:i:s') === $dateEu->format('Y-m-d G:i:s'));