Dogan Ucar

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). 
The “description” attribute enables a brief description which changes has been made with the last modification. 
WP Last Modified shows also the actual revision of and the publication date of the post/page. 
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.
With version 1.1.0, WP Open Last Modified was renamed to WP Last Modified.
Features:
<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]

ggriesser

Optimize the caching behavior of your Website! Smart WordPress by <a href="https://www.velocious.io/" title="Smart WordPress FAQs" rel="nofollow ugc">Velocious.io</a> only reloads pages if something has been changed.
A huge number of users abandon websites that are slow to load. That’s no surprise! No one likes to browse a slow site!
With Smart WP you are able to make your WordPress page load in a better way: Your content gets stored in your visitors browsers and is only reloaded if something changed.
This way you can reduce the performance of your and provide your users with an improved experience.
Your users will love it!
By using Smart WordPress you are able to:
<ul>
<li>change the configuration of your ETags</li>
<li>modify the configuration of the Last-Modified Header</li>
<li>alter the configuration of the Cache-Control Header</li>
</ul>
Acknowledges: This plugin is based on the excellent work by George Notaras. It is a fork of his deprecated Add Headers Plugin – a plugin I have used myself for a bunch of years.

Smart WordPress

Optimize the caching behavior of your Website the easy way and reload pages only if something has been changed.

WP Last Modified vs Smart WordPress