diff --git a/lib/moodlelib.php b/lib/moodlelib.php
index 55cf4e8f840..01f17883a30 100644
--- a/lib/moodlelib.php
+++ b/lib/moodlelib.php
@@ -4767,7 +4767,7 @@ function shift_course_mod_dates($modname, $fields, $timeshift, $courseid) {
     foreach ($fields as $field) {
         $updatesql = "UPDATE {".$modname."}
                           SET $field = $field + ?
-                        WHERE course=? AND $field<>0 AND $field<>0";
+                        WHERE course=? AND $field<>0";
         $return = $DB->execute($updatesql, array($timeshift, $courseid)) && $return;
     }
 
diff --git a/mod/quiz/lib.php b/mod/quiz/lib.php
index 993ca98a30f..4bb74945c57 100644
--- a/mod/quiz/lib.php
+++ b/mod/quiz/lib.php
@@ -1150,8 +1150,14 @@ function quiz_update_events($quiz, $override = null) {
         $addopen  = empty($current->id) || !empty($current->timeopen);
         $addclose = empty($current->id) || !empty($current->timeclose);
 
+        if (!empty($quiz->coursemodule)) {
+            $cmid = $quiz->coursemodule;
+        } else {
+            $cmid = get_coursemodule_from_instance('quiz', $quiz->id, $courseid)->id;
+        }
+
         $event = new stdClass();
-        $event->description = format_module_intro('quiz', $quiz, $quiz->coursemodule);
+        $event->description = format_module_intro('quiz', $quiz, $cmid);
         // Events module won't show user events when the courseid is nonzero.
         $event->courseid    = ($userid) ? 0 : $quiz->course;
         $event->groupid     = $groupid;
@@ -1341,8 +1347,18 @@ function quiz_reset_userdata($data) {
 
     // Updating dates - shift may be negative too.
     if ($data->timeshift) {
+        $DB->execute("UPDATE {quiz_overrides}
+                         SET timeopen = timeopen + ?
+                       WHERE quiz IN (SELECT id FROM {quiz} WHERE course = ?)
+                         AND timeopen <> 0", array($data->timeshift, $data->courseid));
+        $DB->execute("UPDATE {quiz_overrides}
+                         SET timeclose = timeclose + ?
+                       WHERE quiz IN (SELECT id FROM {quiz} WHERE course = ?)
+                         AND timeclose <> 0", array($data->timeshift, $data->courseid));
+
         shift_course_mod_dates('quiz', array('timeopen', 'timeclose'),
                 $data->timeshift, $data->courseid);
+
         $status[] = array(
             'component' => $componentstr,
             'item' => get_string('openclosedatesupdated', 'quiz'),