наверно вы что-то не договариваите ...
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>demo</title>
<script src="http://code.jquery.com/jquery-1.10.2.js"></script>
<script src="http://code.jquery.com/ui/1.11.4/jquery-ui.js"></script>
<link rel="stylesheet" href="http://code.jquery.com/ui/1.11.4/themes/sunny/jquery-ui.css">
<link rel="stylesheet" type="text/css" href="http://fancyapps.com/fancybox/source/jquery.fancybox.css">
<script type='text/javascript' src="http://fancyapps.com/fancybox/source/jquery.fancybox.js"></script>
<script type='text/javascript' src="http://fancyapps.com/fancybox/source/helpers/jquery.fancybox-thumbs.js"></script>
<style type="text/css">
#ui-datepicker-div{
font-size: 12px;
}
#info{
display: none;
}
</style>
<script type='text/javascript'>
$(function () {
$(".test").fancybox({
type: 'inline'
});
$('input[name="tags"]').datepicker();
});
</script>
</head>
<body>
<a class="test" href="#info" >go fancyboxinfo</a>
<div id="info">
<input id="text_tag_input" type="text" name="tags" />
</div>
</body>
</html>