Checkout Date Field

Hi all, just a fast question.

I follow the tutorial for add custom fields on checkout process:
http://docs.woothemes.com/document/tutorial-customising-checkout-fields-using-actions-and-filters/
All works fine with text and select field but…
How can I add a simple date field (dd/mm/Y)?

Thanks in advance

http://wordpress.org/extend/plugins/woocommerce/