--- manager/customers.php.orig	2004-10-16 20:06:13.000000000 +0200
+++ manager/customers.php	2004-10-16 20:07:39.000000000 +0200
@@ -57,7 +57,9 @@
         }
 
         if (ACCOUNT_DOB == 'true') {
-          if (checkdate(substr(tep_date_raw($customers_dob), 4, 2), substr(tep_date_raw($customers_dob), 6, 2), substr(tep_date_raw($customers_dob), 0, 4))) {
+          // WS - date internationalization fix
+          $notused = array();
+          if (tep_checkdate($customers_dob, DOB_FORMAT_STRING, &$notused) == false) {
             $entry_date_of_birth_error = false;
           } else {
             $error = true;