WP Minor Edit

This plugin adds a checkbox labelled “Minor edit” to the post editing
page of WordPress. If you check that box, the post’s last-updated date
is left unchanged when you save the post.

For full details, see the plugin page

License: GPL v3

1. Download and extract the zip file.
2. Upload the plugin directory to /wp-content/plugins on your server.
3. Go to the Plugins screen in your WordPress Admin and activate it.

Why do I care?

Because your readers do.

If you are making minor changes (spelling corrections, category updates) to old posts
without this plugin, your posts will be marked with a new updated date in your atom
feed. Readers will then see your posts reappearing in their feed readers. Additionally,
if your posts are syndicated (e.g. using Planet or Venus) they will reappear at the
top of the page.

Can’t this be done automatically?

It is difficult to conceive of an algorithm that can correctly decide what constitutes
a minor edit. Ultimately it is your decision as the author, based on whether or not
the change you’re making requires the reader’s attention again.

1. 

   The checkbox!