You don't look like calling the actual countdown script as indicated on the website you took the script from:
~2. Download and include the jQuery Countdown CSS and JavaScript in the head section of your page.
<link rel="stylesheet" type="text/css" href="css/jquery.countdown.css">
<script type="text/javascript" src="js/jquery.plugin.js"></script>
<script type="text/javascript" src="js/jquery.countdown.js"></script>
EDITED: Other than that, check the developer tool of your browser for errors and try to fix them all. They might not be related directly to this, but they may prevent the execution of the rest of the script.