diff --git a/cara/apps/calculator/static/js/form.js b/cara/apps/calculator/static/js/form.js
index c842c8d2..6b5fa2c3 100644
--- a/cara/apps/calculator/static/js/form.js
+++ b/cara/apps/calculator/static/js/form.js
@@ -123,6 +123,8 @@ function require_air_supply(option) {
 
 function require_single_event(option) {
   $("#single_event_date").prop('required', option);
+  if (!option)
+    removeInvalidDate();
 }
 
 function require_recurrent_event(option) {
@@ -309,8 +311,6 @@ $(document).ready(function () {
   $(".finish_time").change(function() {validateFinishTime(this)});
   $(".start_time").change(validateStartTime);
 
-  $("#event_type_recurrent").change(removeInvalidDate);
-
   var radioValue = $("input[name='event_type']:checked");
   if (radioValue.val()) {
     require_fields(radioValue.get(0));