public function getLastUpdatedAt()
    {
        $qb = $this->createQueryBuilder('p');

        $date = $qb
            ->select('p.updatedAt')
            ->addOrderBy('p.updatedAt', 'DESC')
            ->getQuery()
            ->setMaxResults(1)
            ->getSingleScalarResult();

        if (null !== $date) {
            return new \DateTime($date);
        }

        return null;
    }