Description:
------------
---
From manual page: http://www.php.net/class.datetime
---

It appears that creating a datetime object via createFromFormat and using DATEATOM support short year format, like 20-01-01T15:15:15Z.

This isn't matching format which is Y-m-d\TH:i:sO and should return false.

Doc for Y string format : 
+ A full numeric representation of a year, 4 digits

Test script:
---------------
<?php
$d = DateTime::createFromFormat(DATE_ATOM, "20-01-01T01:01:01Z");
var_dump($d); // should return false