How to stop comments after a certain date

See: https://codex.www.ads-software.com/Settings_Discussion_Screen

Automatically close comments on articles older than [X] days – Check the box and enter the number of days (e.g. 14 days) after which WordPress will automatically flag eligible posts so that no more comments are accepted.

No plugin required!

thanks for your reply, but the issue I’ve got is my site is custom and posts are added by contributors.

I have look at another mod which seems to do what I want apart from this mod deletes the post once a date is reached using the below code

wp_delete_post ($a->post_id);

Can anyone advice me what I should replace the above to turn off “add comments” so no further comments can be added?

thanks Mally

Without seeing the surrounding code, you could try replacing that line with;

$exp_post = array();
$exp_post['ID'] = $a->post_id;
$exp_post['comment_status'] = 'closed';
$exp_post['ping_status'] = 'closed';
wp_update_post( $exp_post );