Si ocupa un datepicker, aqui como integrarlo sencillamente;
<!DOCTYPE html>
<html>
<head>
<link href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/themes/base/jquery-ui.css" rel="stylesheet" type="text/css"/>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.5/jquery.min.js"></script>
<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/jquery-ui.min.js"></script>
<script>
$(document).ready(function() {
$("#datepicker").datepicker({
defaultDate: document.forms['myForm'].elements['dateSelected'].value,
onSelect: function(dateText, inst) {
alert (dateText);
document.forms['myForm'].elements['dateSelected'].value = dateText;
}
});
});
</script>
</head>
<body style="font-size:62.5%;">
<form name=...