--- /dev/null
+/**
+ * Implements hook_validate().
+ */
+function {{ machine_name }}_validate($node, $form, &$form_state) {
+ if (isset($node->end) && isset($node->start)) {
+ if ($node->start > $node->end) {
+ form_set_error('time', t('An event may not end before it starts.'));
+ }
+ }
+}