diff --git a/mod/data/field/date/field.class.php b/mod/data/field/date/field.class.php
index 9717faec041..1a92a12a593 100755
--- a/mod/data/field/date/field.class.php
+++ b/mod/data/field/date/field.class.php
@@ -83,7 +83,8 @@ class data_field_date extends data_field_base {
     }
 
     function get_sort_sql($fieldname) {
-        return 'CAST('.$fieldname.' AS unsigned)';
+
+         return sql_cast_char2int($fieldname, true);
     }