diff --git a/mod/quiz/jstimer.php b/mod/quiz/jstimer.php
index b88977fe907..1a0d7641a39 100644
--- a/mod/quiz/jstimer.php
+++ b/mod/quiz/jstimer.php
@@ -12,6 +12,12 @@ var timesup = "<?php print_string("timesup","quiz");?>";
 var quizclose = <?php echo ($quiz->timeclose - time()) - $timerstartvalue; ?>; // in seconds
 var quizTimerValue = <?php echo $timerstartvalue; ?>; // in seconds
 parseInt(quizTimerValue);
+
+// @EC PF : client time when page was opened
+var ec_page_start = new Date().getTime();
+// @EC PF : client time when quiz should end
+var ec_quiz_finish = ec_page_start + <?php echo ($timerstartvalue * 1000); ?>;
+
 // -->
 </script>
 <script language="javascript" type="text/javascript" src="timer.js"></script>
diff --git a/mod/quiz/timer.js b/mod/quiz/timer.js
index bdb9e960fe5..a45284424ab 100644
--- a/mod/quiz/timer.js
+++ b/mod/quiz/timer.js
@@ -6,7 +6,12 @@
 //
 function countdown_clock(theTimer) {
     var timeout_id = null;
-    quizTimerValue = quizTimerValue - 1;
+
+	// @EC PF : current client time
+	var ec_now_epoch = new Date().getTime();
+
+	// @EC PF : time left according to client
+	quizTimerValue = Math.floor( (ec_quiz_finish - ec_now_epoch) /1000 );
 
     if(quizTimerValue == 0) {
         clearTimeout(timeout_id);