--- scheduler.module	2013-07-27 18:42:28.000000000 +0100
+++ scheduler.module	2013-09-08 16:55:31.000000000 +0100
@@ -336,6 +336,9 @@ function scheduler_form_alter(&$form, $f
         );
       }
 
+      // Do not perform any validation when the Delete button is clicked.
+      $form['actions']['delete']['#limit_validation_errors'] = array();
+
       $description_format = t('Format: %time.', array('%time' => format_date(time(), 'custom', $date_format)));
       if ($publishing_enabled) {
         $description_blank = '';