Make sure the head section of the template has the following lines

 <link rel="stylesheet" href="/styles/dhtmlgoodies_calendar.css" media="screen" />
<script  type="text/javascript" src="/javascript/dhtmlgoodies_calendar.js"></script>

if you did install the package in the base directory you will need to add the name of the sub directory

after the  href="/ and the src="/ example if you installed in a directory called hotels

<script  type="text/javascript" src="/hotels/javascript/dhtmlgoodies_calendar.js"></script>