"30 February" passes client side vaildation in Date field on Webform

The Date "30 February XXXX" isn't a valid date. But if i use a Date field on a Webform, client side validation doesn't throw an error. The error is signaled only server side, when you submit the form.
I think this is not a rigth behaviour.
It happens with 31 February and 29 February (on non leap year), too.