How does redirect work when publish date changes and date in url changes?

For example I create post at 29 day, publish it. In url there is 29 day. Now if I change publish date to 28, url works with 28 day. But it also works with 29 day, just redirects to 28.

I do not get how it knows how to redirect to 28? Will it be forever? I see lot of articles telling not to change publih dates. Why? If it redirects, then it is good - old and new links work. How does it work? I could not see in where the links are saved, wp_links table is empty. Where does it store information where to redirect to?