In a year filled with bad news, October 1 and 2, 2017 were particularly bad. First came state violence in the referendum for Catalan independence. This was followed by the worst mass shooting in U.S. history, which left 59 people dead and more than 520 injured. Then the rock musician Tom Petty suffered a heart attack which eventually killed him.

All three incidents unfolded — as all incidents do — as a sequence of events in time.

Seeing news items in chronological order is key to understanding what happened. But you wouldn’t necessarily be able to follow along if you were reading about them in social media like Facebook and Twitter.

This is because these information environments present posts in a sequence determined by algorithms (ostensibly) designed to keep you engaged.

Under normal conditions, you may not care about reading the latest posts in the order they were published. For example, you may have a very chatty aunt who incessantly posts photos of her grandchildren; in a strictly chronological news feed, your aunt’s posts would often dominate your feed, turning you off from the platform. Changing the sequence of posts to an “interest”-based order (where interest is somehow determined by algorithms based on your profile, preferences, and behavior) allows other voices to break through her posts.

This non-chronological approach fails spectacularly when you want to learn the latest information about a story.

For example, on the evening of October 1 — when the massacre was unfolding in Las Vegas — a friend of mine posted on Facebook asking what was going on there and whether or not it was a mass shooting. This was a reasonable thing to ask as the event was happening. However, it didn’t seem reasonable the day after the incident had played itself out and everyone knew that yes, in fact, it was a mass shooting. Alas, this (Oct 2) is when Facebook showed me my friend’s post as though it was “news.” (I use the word “news” in quotes, but Facebook itself calls the place where you see your friends’ posts the “news feed.” To me, “news” implies that you’re going to be seeing the latest, which isn’t the case on​ Facebook.)

Twitter also fails the breaking news test, but for different reasons. Although it also messes around with the sequence of posts (by starting their news feed with an “in case you missed it” section that is algorithmically determined), the main issue with Twitter is that the “freshness” of posts in the timeline can be affected by whether or not they are retweeted. So if I follow you, and you retweet post from two days ago, it will appear at the top of my timeline as the newest thing. This was the case with Petty’s death: The earliest reports said the singer had suffered cardiac arrest, then CBS (a credible source) reported he’d died, then they retracted the story. All the while, the earlier reports of the singer dying were being retweeted, along with condolences from other celebrities. This led to a situation of uncertainty and confusion. (Alas, Mr. Petty succumbed later in the day.)

Twitter bills itself as “what’s happening in the world," but in an emerging urgent situation neither it or Facebook works​ very well to keep us informed.

An algorithmically determined feed can be more engaging under normal circumstances, but simple chronological order — showing the most recent items first — would serve us much better at times we need to learn the latest.

This may call for something like a “breaking news” mode that switches the UI in these environments​ from the algorithmically-determined order to something simpler. In times such as these, this may even be the more engaging approach.