diff --git a/UsedCars/Test_classes/Staff/UsedCars_Test_Staff.php b/UsedCars/Test_classes/Staff/UsedCars_Test_Staff.php
index fcc4300..d998981 100644
--- a/UsedCars/Test_classes/Staff/UsedCars_Test_Staff.php
+++ b/UsedCars/Test_classes/Staff/UsedCars_Test_Staff.php
@@ -50,7 +50,7 @@
             'DATE_OF_BIRTH'     =>  array(  'generic_type'  =>  'DATE',
                                             'sql_type'      =>  array( 'DATE' ),
                                             'nullable'      =>  false,
-                                            'underflow'     => "SYSDATE - TO_YMINTERVAL( '18-0' ) - 1",
+                                            'underflow'     => "SYSDATE - TO_YMINTERVAL( '18-0' ) + 1",
                                             'test_value'    =>  "TO_DATE( '2012-03-28', 'YYYY-MM-DD' )" ),
         );
     }