I needed a datefield like 'dd/mm/yyyy' or so with textfield.
My solution in Class.Validator.php
<?php
function DateText($value)
{
//Date d/m/yyyy and dd/mm/yyyy
//1/1/00 through 31/12/99 and 01/01/1900 through 31/12/2099
//Matches invalid dates such as February 31st
$regex='^\b(0?[1-9]|[12][0-9]|3[01])[- /.](0?[1-9]|1[012])[- /.](\d{4})\b^';