You need a form tag on your web page for that and the datepicker will have to be on that form, then you can decide to use method POST or method GET.
<form method="POST" ... >
</form>
I'm very sure this doesn't answer your question, but you need to learn how to ask more specific questions ;) Feel free to edit your question to reveal what it is exactly you're trying to accomplish .
Cheers
Manfred