public function cleanRecentWorkspaces()
    {
        $this->log('Cleaning recent workspaces entries that are older than six months');

        /** @var WorkspaceRecentRepository $recentWorkspaceRepo */
        $recentWorkspaceRepo = $this->om->getRepository('ClarolineCoreBundle:Workspace\WorkspaceRecent');
        $recentWorkspaceRepo->removeAllEntriesBefore(new \DateTime('-6 months'));
    }