Edit in JSFiddle

<script type="text/javascript" src="http://ajax.microsoft.com/ajax/jquery.ui/1.8.5/jquery-ui.js"></script>
<script type="text/javascript" src="calendario.js"></script>
<link type="text/css" rel="Stylesheet" href="http://ajax.microsoft.com/ajax/jquery.ui/1.8.5/themes/redmond/jquery-ui.css" />
<form action="/" method="post">
<label for="calendario">Data</label>
<input id="calendario" type="text" name="calendario" />
</form>