This plugin generates customizable messages stating the last modification date and time for the whole site and the individual content (if appropriate)
No. As long as your template has one of the following lines of code in the footer.php file:
<?php do_action('wp_footer'); ?> <?php wp_footer(); ?>
Then the plugin can use a built in WordPress hook to automatically insert the information into your website. This should work with 99% of themes based on normal WordPress rules.
Additionally, the included widget can be used to insert the information in a sidebar or there are two plugin functions available to generate the output anywhere that PHP can be executed:
<?php lmf_generate_unformatted_output(); ?> <?php lmf_generate_formatted_output(); ?>
If you are having problems then you can ask questions, leave comments or find more information at the plugin's homepage: Last Modified Footer.