I gave Google an off-by-one birth date way back when. A few years ago they figured it out -- sorry, don't recall what hints they may have been working from --

I gave Google an off-by-one birth date way back when. A few years ago they figured it out -- sorry, don't recall what hints they may have been working from -- and demanded a correction. After considering the implicit threat, account termination, I surrendered the actual birthdate.