Fire up Google search to find the normal Google logo replaced with a cheery picture of cakes and a “Happy Birthday” message. How do they know? I am frightened. 😕

It only knows what you have told it…

You have a gmail/google account and put in your DOB somewhere?

It was just a lucky guess

Happy Birthday btw….

How do I know that?! 😯

It can see you wearing your party hat via your webcam.

I’m sure someone will post up the URL that shows you everywhere you’ve been on google maps. (don’t have a shortcut on the browser, and my memory is not as good as google)
(edit: maps.google.com/locationhistory that’s the one )

happy birthday.

if you have a gmail / google / youtube / picassa account use those credentials to log into Google Dashboard. A pretty helpful summary of what they know. You can edit or delete from there as well.