diff --git a/chrono/manager/templates/chrono/manager_time_period_exception_form.html b/chrono/manager/templates/chrono/manager_time_period_exception_form.html
index 0456588e..15dd4fd4 100644
--- a/chrono/manager/templates/chrono/manager_time_period_exception_form.html
+++ b/chrono/manager/templates/chrono/manager_time_period_exception_form.html
@@ -35,5 +35,16 @@
     <button class="submit-button">{% trans "Save" %}</button>
     <a class="cancel" href="{% url 'chrono-manager-agenda-settings' pk=desk.agenda.id %}">{% trans 'Cancel' %}</a>
   </div>
+
+  {% if not object.id %}
+  <script>
+  $('[name="start_datetime$date"]').on('change', function() {
+    var $end_datetime = $('[name="end_datetime$date"]');
+    if (! $end_datetime.val()) {
+      $end_datetime.val($(this).val());
+    }
+  });
+  </script>
+  {% endif %}
 </form>
 {% endblock %}