A Christmas #zf2 easter egg

Module.php

<?php

namespace EasterEgg;

use DateTime;

class Module
{
    public function onBootstrap(MvcEvent $e)
    {
        $today     = new DateTime;
        $christmas = new DateTime('2013-12-24');
        $diff      = $today->diff($christmas);

        if ($diff->days !== 0) {
            return;
        }

        $app      = $e->getApplication();
        $response = $app->getResponse();
        $headers  = $response->getHeaders();

        $headers->addHeaderLine('X-HoHoHo', 'Merry Christmas!');
    }
}