- date_diff: documentation ( source)
- var_dump: documentation ( source)
- date_default_timezone_set: documentation ( source)
<?php
echo PHP_VERSION;
date_default_timezone_set('UTC');
$dti = new DateTimeImmutable('2012-01-01 00:00:00');
$dt = new DateTime('2012-01-01 00:01:00');
var_dump($dt->diff($dti), date_diff($dt, $dti));