fixes #3637

Closes #3637

Merge request studip/studip!2518

app/controllers/admin/courses.php

@@ -643,7 +643,9 @@ class Admin_CoursesController extends AuthenticatedController
             $d['contents'] .= '</ul></div>';
         }
         if (in_array('last_activity', $activated_fields)) {
-            $d['last_activity'] = strftime('%x', lastActivity($course->id));
+            $last_activity = lastActivity($course->id);
+            $d['last_activity'] = strftime('%x', $last_activity);
+            $d['last_activity_raw'] = $last_activity;
         }
 
         foreach (PluginManager::getInstance()->getPlugins('AdminCourseContents') as $plugin) {

resources/vue/components/AdminCourses.vue

@@ -246,6 +246,9 @@ export default {
                 return collator.compare(striptags(a[sortby]), striptags(b[sortby]));
             };
 
+            if (sortby === 'last_activity') {
+                sortFunction = (a, b) => a.last_activity_raw - b.last_activity_raw;
+            } else {
                 let is_numeric = true;
                 for (let i in array) {
                     if (striptags(array[i][sortby]) && isNaN(striptags(array[i][sortby]))) {
@@ -259,6 +262,7 @@ export default {
                             - (striptags(b[sortby]) ? parseInt(striptags(b[sortby]), 10) : 0);
                     };
                 }
+            }
 
             // Actual sort on copy of array
             return array.concat().sort((a, b) => directionFactor * sortFunction(a, b));