diff --git a/index.php b/index.php
index 8b9da01..823f546 100644
--- a/index.php
+++ b/index.php
@@ -206,7 +206,13 @@
 
     // Commit transaction and finish up.
     $transaction->allow_commit();
+
+    // Rebuild all course cache / calendar dates
     rebuild_course_cache($course->id);
+    $task = new \core\task\refresh_mod_calendar_events_task();
+    $task->set_custom_data(array('courseid' => $course->id));
+    \core\task\manager::queue_adhoc_task($task, true);
+
     redirect($PAGE->url, get_string('changessaved'));
 }
 
diff --git a/mod/forumdates.php b/mod/forumdates.php
index 82815e8..8e3d2c6 100644
--- a/mod/forumdates.php
+++ b/mod/forumdates.php
@@ -67,4 +67,17 @@ public function validate_dates(cm_info $cm, array $dates) {
         }
         return $errors;
     }
+
+    public function save_dates(cm_info $cm, array $dates) {
+        global $DB, $COURSE, $CFG;
+        parent::save_dates($cm, $dates);
+
+        require_once($CFG->dirroot.'/mod/forum/locallib.php');
+        $forum = $DB->get_record('forum', ['id' => $cm->instance]);
+        $forum->cmidnumber  = $cm->id;
+
+        // Update the calendar and grades.
+        forum_update_calendar($forum, $cm->id);
+        forum_grade_item_update($forum);
+    }
 }