Description:
------------
adding P1D to 2369-12-30 00:00:00 the result is 2370-01-00
really strange day :oD

Test script:
---------------
---
From manual page: http://www.php.net/datetime.add
---

$a = new DateTime("2369-12-30 00:00:00");
$a->add(new DateInterval('P1D'));
var_dump($a);

will print

class DateTime#3 (3) {
  public $date =>
  string(26) "2370-01-00 00:00:00.000000"
  public $timezone_type =>
  int(3)
  public $timezone =>
  string(11) "Europe/Rome"
}