- var_dump: documentation ( source)
- date: documentation ( source)
- strtotime: documentation ( source)
<?php
$occurenceDate = '2012-05-06 13:32:00';
$dt = new \DateTime( date('Y-m-d H:i:s' , strtotime( $occurenceDate ) ) , new \DateTimeZone( 'GMT' ) );
var_dump($dt);
$dt->modify('+561 days');
var_dump($dt);