Lots of people have said this, but Facebook has upload directly from phones to their server, right? So I would be shocked if they aren't trusting the time tags from direct uploads and metadata set by the camera (which they strip before displaying, but surely they ingest it) more than they trust upload times.
Also, people tag themselves all the time, and if you upload a photo with people, you can tell quickly that they already identify people with high accuracy, because they suggest tags for you.
Also, people tag themselves all the time, and if you upload a photo with people, you can tell quickly that they already identify people with high accuracy, because they suggest tags for you.