How People Can Use Facebook To Track Your Sleep Patterns

You get ready for bed, you check Facebook. You wake up, you check Facebook. Both times, and every time, Facebook knows.

And if you've ever checked Facebook Messenger to see if someone's still awake, you may have noticed how spot-on it can be. So a Danish coder named Søren Louv-Jansen built a simple program that gathers up the digital receipts left behind when Facebook says someone was "last active," and was able to see a makeshift sleep schedule of all of his friends.