I personally use the very good http://www.datejs.com/ library.
Docco here: http://code.google.com/p/datejs/wiki/APIDocumentation
You can use the following to get your Australian format and will validate the leap day 29/02/2012 and not 29/02/2011:
jQuery.validator.addMethod("australianDate", function(value, element) {
return Date.parseExact(value, "d/M/yyyy");
});
$("#myForm").validate({
rules : {
birth_date : { australianDate : true }
}
});
I also use the masked input plugin to standardise the data http://digitalbush.com/projects/masked-input-plugin/
$("#birth_date").mask("99/99/9999");