Fatal error: Call to undefined method DateTime::diff() in /home/content/15/7899515/html/wp-content/

Fatal error: Call to undefined method DateTime::diff() in /home/content/15/7899515/html/wp-content/plugins/wp-defender/app/module/audit-log-module/component/class-wd-audit-api.php on line 54

What can i do to fix that?