When people post a link, a Facebook bot looks at the content and finds the content of the <title> tag and creates a summary. My modest proposal is that it also locates the post datestamp to include here.
Every Facebook post has the name of the poster with when they posted it. It might be “Just now” to minutes or hours then if more than a day, the date. Then if more than a year, how many.
If Mark posts an article from 2 years ago right now, then it can appear fresh and new. Facebook also scrubs URLs so that if that indicated the publication date, one must click through to know that it is old. And, we all know in general people re-share things without doing such due diligence. This could be part of why missing persons posts get shared years after the person was found as people have no idea that the article is 1-10 years old without clicking through.
From Facebook Feature Request: External content datestamp published March 04, 2019 at 07:41AM.