Indeed but when I posted the pics it was 2 years later from a totally different continent and no reference to the location on the photos.

right, but assuming the timestamp is on the photos, facebook still knows where you were at the time they were taken. The time you upload them is immaterial

> In your opinion, how would Facebook know your location if you never logged in from a GPS-enabled smart phone? (and never approved an HTML5 geo permission request on your laptop).

No real trick to that; if the user signs in from an IP leased to a Christchurch, NZ ISP on March 5th, 2007, then it's a safe bet that any photos taken that day were taken near Christchurch (and you get date taken from the EXIF data of virtually every camera on the planet).

well they can do a best guess based on the location of your IP, even if you only sign into facebook once while you're travelling. The really interesting question is: can they do this even if you have not signed into facebook at all on your travels, or for totally new accounts with no location history at all.

If they can, then they must be doing image recognition in some way. Perhaps someone who has more time / energy than me could try this by creating a new account and uploading some photos of recognisable objects (but without exif geo data).

Facebook knows more about me than I do. I'd be interested in their history file of my location.

When you were in NZ: [hh:mm dd/mm/yyyy, nz.ip.address] => [hh:mm dd/mm/yyyy, location]

When you uploaded the photos: [hh:mm dd/mm/yyyy, photo] + above data => [photo, location]