Post Updated NG (NG stands for “Next Generation”) is a WordPress plugin that displays the last modified date and time for a post (that is, if later than the original post date). Useful for providing a “last updated” flag to your posts. It is based on the plugins of Ronald Huereca and Kaf Oseo.
To install and use it, download the zip file, extract
post-updated-ng.php, upload this to your
wp-content/plugins/ directory, activate the plugin in WordPress then (optionally) set its options in the ‘Options’ menu in WordPress.