Does anyone know if I can use a php include as standard in a Joomla 1.5 module? Or do I have to download a Joomla extension such as Jumi or some other plugin to allow includes to work?

I have posted on Joomlas' forum but had no replies which really answer my question.

Basically I have designed my site in HTML/CSS and have used a php include on every page to provide a TIMESTAMP of when each page was last updated.

Now I am beginning the process of adding Joomla managed content to my site and I am trying to add my php timestamp include to display on my pages as a Joomla module.

The html code which I currently use on my pages to call the include is -
Code:
<p id="timestamp"><?php include("../timestamp.php"); ?></p>
and the actual timestamp.php code is -
PHP Code:
<?php echo "This page was last modified on: " date ("F d Y H:i:s."getlastmod());?>
If I add the code include to the timestamp.php file in my joomla module, the timestamp does not work.