Displaying the post’s update date

Place this code in your home.php file:

<p>Last modified: <?php the_modified_date(); ?></p>

I couldn’t find a Home.PHP in any of the Graphene directories, or elsewhere.

OK, found it.
For posts – I placed the code in the loop-single.php file.

Great, glad you solved it.

Use a child theme for that. Any changes you make to the theme will be overridden during an update.