it would help if you could name the theme you are using or if you post the code of your footer.php.
generally, you could use something like:
<p>@copyright 2009-<?php echo date('Y'); ?></p>
Thanks. When I went back to copy the code in my footer.php to respond, I also went back into my theme, and there it was, right in front of me, in plain English — a field for copyright where all I had to do was add 2010. I’d looked at this page three times without seeing it. Thanks for your help, though, because ultimately it led me to look with different eyes.