You can select a jquery gallery custom scheme nearest to your page/form design (or build and download your own) from jquery's 'theme roller'.
Just place the scripts in same folder as existing ones and link to them from your page (or just rename them to the same as existing).
There are a couple of examples I did HERE
and a sample contact form with custom date-picker HERE
(If you click on the 'Home' link, you can download the mini-site files and customised date-picker code in-situ HERE - click the 'Contact' link for the page with the form with date picker implemented.)