Replace remaining functions in include/datetime by Temporal methods

- Fix uses statements

mod/ping.php

@@ -15,6 +15,7 @@ use Friendica\Database\DBM;
 use Friendica\Model\Contact;
 use Friendica\Model\Group;
 use Friendica\Util\DateTimeFormat;
+use Friendica\Util\Temporal;
 use Friendica\Util\XML;
 
 require_once 'include/datetime.php';
@@ -370,7 +371,7 @@ function ping_init(App $a)
 					'name'      => $notif['name'],
 					'url'       => $notif['url'],
 					'photo'     => $notif['photo'],
-					'date'      => relative_date($notif['date']),
+					'date'      => Temporal::getRelativeDate($notif['date']),
 					'message'   => $notif['message'],
 					'seen'      => $notif['seen'],
 					'timestamp' => strtotime($local_time)