[Nextgrid]

The "Off-Facebook Activity" page is reasonably new however the data it shows goes back years, suggesting the data collection itself has been going on for a long time and Facebook has now become generous enough to let you know about it.

There's reason to believe even more data is being collected & processed behind the scenes but they don't tell you (yet?).

[iamacyborg]

This stuff has been collected for as long as Facebook have offered pixels, widgets and SDK's for webmasters and devs to use on their sites/apps.