Problems
1. You have included the jQuery files two times. Remove one.
<script src="../../Scripts/jquery-1.7.1.js" type="text/javascript"></script>
<script src="../../Scripts/jquery-1.7.1.min.js"type="text/javascript"></script>
2. You have included jQuery UI js two times. Remove one.
<script src="../../Scripts/jquery-ui-1.8.20.js" type="text/javascript"></script>
<script src="../../Scripts/jquery-ui-1.8.20.min.js" type="text/javascript"></script>
3. You have included jQuery UI css two times. Remove one.
<link href="@Url.Content("~/Content/themes/base/jquery.ui.all.css")" rel="stylesheet" type="text/css" />
<link href="@Url.Content("~/Content/themes/base/jquery.ui.css")" rel="stylesheet" type="text/css" />
Solution
Refer -
Datepicker[
^]
Check what are the files included and how it is working. Try like below...
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>jQuery UI Datepicker - Default functionality</title>
<link rel="stylesheet" href="http://code.jquery.com/ui/1.10.3/themes/smoothness/jquery-ui.css" />
<script src="http://code.jquery.com/jquery-1.9.1.js"></script>
<script src="http://code.jquery.com/ui/1.10.3/jquery-ui.js"></script>
<link rel="stylesheet" href="/resources/demos/style.css" />
<script>
$(function() {
$( "#datepicker" ).datepicker();
});
</script>
</head>
<body>
<p>Date: <input type="text" id="datepicker" /></p>
</body>
</html>