diff --git a/app/controllers/admin/courses.php b/app/controllers/admin/courses.php
index afa12c960c061e760f3923883957f0f3d07bc107..03e447c415ccb36ca0a6803161dbecc1a1a4c233 100644
--- a/app/controllers/admin/courses.php
+++ b/app/controllers/admin/courses.php
@@ -604,7 +604,7 @@ class Admin_CoursesController extends AuthenticatedController
             $d['contents'] .= '</ul></div>';
         }
         if (in_array('last_activity', $activated_fields)) {
-            $d['last_activity'] = date('%x', lastActivity($course->id));
+            $d['last_activity'] = strftime('%x', lastActivity($course->id));
         }
 
         foreach (PluginManager::getInstance()->getPlugins('AdminCourseContents') as $plugin) {