--- a/date/date.devel_generate.inc
+++ b/date/date.devel_generate.inc
@@ -10,6 +10,8 @@
  * Included only when needed.
  */
 function date_devel_generate($node, $field, $instance, $bundle) {
+  module_load_include('inc', 'date_api', 'date_api_elements');
+  
   $node_field = array();
   if (isset($instance['widget']['settings']['year_range'])) {
     $split = explode(':', $instance['widget']['settings']['year_range']);