jackalope/jackalope — comment on commit 272b6728b21ba2092e00eee6e859e31bb577fc06
File: src/Jackalope/Version/Version.php line 38
By dbu:

either use ->getDate() (see http://phpcr.github.com/doc/html/phpcr/propertyinterface.html#getDate() ) or just $this->getPropertyValue('jcr:created')