please consider this as a replacement for the dateISO validation. The new regular expression comes from here:

http://regexlib.com/REDetails.aspx?regexp_id=2092

and checks for ISO date format. The old method would allow things like 2009-31-31 and 2009-02-31

dateISO: function(value, element) {

return this.optional(element) || /^(\\d{4}(?:(?:(?:\\-)?(?:00[1-9]|0[1-9][0-9]|[1-2][0-9][0-9]|3[0-5][0-9]|36[0-6]))?|(?:(?:\\-)?(?:1[0-2]|0[1-9]))?|(?:(?:\\-)?(?:1[0-2]|0[1-9])(?:\\-)?(?:0[1-9]|[12][0-9]|3[01]))?|(?:(?:\\-)?W(?:0[1-9]|[1-4][0-9]5[0-3]))?|(?:(?:\\-)?W(?:0[1-9]|[1-4][0-9]5[0-3])(?:\\-)?[1-7])?)?)$/.test(value);

}