Dogan Ucar

<p>WP Last Modified adds the ‚last_modified_date‘ shortcode to your WordPress installation. This shortcode shows the last timestamp of your post/page. Simply use the „format“ attribute for custom date formats (it uses PHP’s date() function).<br />
The “description” attribute enables a brief description which changes has been made with the last modification.<br />
WP Last Modified shows also the actual revision of and the publication date of the  post/page.<br />
You can customize the text which will be shown under each post/page under settings -> WP Last Modified Settings. You can also hide one of the elements if you do not want them.</p>
<p>With version 1.1.0, WP Open Last Modified was renamed to WP Last Modified.</p>
<p>Features:</p>
<ul>
<li>last modification timestamp of a post/page</li>
<li>publication timestamp of a post/page</li>
<li>timestamp format customizable</li>
<li>revision count</li>
<li>custom text with placeholders</li>
<li>last modification description</li>
<li>excluding single posts/pages from displaying the last modification timestamp</li>
</ul>


WP Last Modified

This plugins adds the last modified date, current revision and the publication date of your post/page. Simply use the shortcode [last_modified_date]

djuric

<p>Using this plugin you can easily change or prevent updating the last modified date for each post. Controlling the last modified date can come in handy when you would like to control “order by last modified” for posts (or custom post type).</p>
<p>When this plugin is active it will enable Last modified date options in Status & Visibility panel in sidebar. Changing the modified date can be done by clicking the date link and selecting a new date for the post. It’s also possible to disable future updates of the last modified date by setting the “Freeze modified date” option to on.</p>
<h4>Custom post types support</h4>
<p>To update the last modified date, plugin is using “rest_pre_insert_{$post_type}” hook which is executed before “init” where other custom post types are usually registered. This is the reason why plugin is not aware of any additional post types other than those registered by WordPress core. To support additional post types you can add constant in following format to wp-config.php:</p>
<pre><code>define( 'CLM_DATE_POST_TYPES', ['post-type-slug-1', 'post-type-slug-2'] );
</code></pre>
<p>Custom post types are also required to have “custom-fields” support declared.</p>
<h4>Support</h4>
<p>For support or code contributions please refer to <a href="https://github.com/djuric/change-last-modified-date" rel="nofollow ugc">Github repo</a>.</p>


Change Last Modified Date

Do not work with gutenberg.

Would love to use this plugin, but it doesn't work with the "classic editor" anymore. The author suggests using an earlier release, but I went back to version 1.3 and 1.2, and neither of them worked for me either. 

I code and manage a lot of commercial websites, and none of them uses Gutenberg, it's too easy for clients to mess up sites with it.

Currently does not work with classic editor

Change or prevent updating Last Modified date for individual posts.

WP Last Modified vs Change Last Modified Date