[whonut]

The only place I can see it getting info like this is a social network, and that means G+...

In all seriousness, could they cross-reference dates in G+ posts and photos to see that you mentioned being on your honeymoon when it was taken? Seems like something they'd do if G+ was actually a thing people used.

[icebraining]

There's the Google Search looking for good place to stay on a honeymoon, the email or hangout message sent to the SO mentioning it, the calendar event, etc.

Even just seeing that you're on an irregular stay in Thailand (which it got from your Android) right after your marriage can be telling.

[whonut]

Completely forgot email, calendar etc.

D'oh.

[walterbell]

Other options are

  Gmail
  Calendar
  SMS
  "Now on Tap" can MiTM content of every Android app

[notatoad]

They've got most people's email and calendar, that's a lot more data than G+.

[jbuzbee]

I am seeing that it uses tags and faces that I previously put on photos within iPhoto and are evidently stored with Exif. So if you used iPhoto to tag your set "honeymoon" it will pick that up.

[wstrange]

Or they can analyse the photo itself. They seem to be getting quite good at picking out faces, scenes, events, and locations in photos.