Hi there!
That would require some coding skills. I’ll give you a brief explanation of where you need to edit the theme. If you need more help, you should ask your question at the general WordPress forum because it’s not specific to the theme.
So, at first, you need to have a child theme. Download at https://coldbox.miruc.co/ and set up.
In the child theme, create a directory named “parts”, and create a file “related-posts.php” under the directory. Copy the content found in https://raw.githubusercontent.com/mirucon/coldbox/c743194a56f020d8defcc5cf9e7d1c258febb08f/parts/related-posts.php and paste it to the file.
There are 3 points you need to edit to achieve the goal. These are around line 32, 60, and 80.
They are the queries used for [WP_Query](https://developer.www.ads-software.com/reference/classes/wp_query/parse_query/) class. And with date_query parameter, you can limit the created or updated date of posts. For the detail of how you use date_query, you need to find out by yourself (I have never used that before actually).
