Just a rhetorical question--Why when you ask someone their age, so many answer with "I'll be XX in XX days". So that makes them XX - 1. Why don't they just say what they are now?
Maybe a subconscious left-over from youth when you wanted to be older - I'm 6 1/2? Or maybe they are just trying to be honest, thinking that they are close to that. Maybe it would be easier if we aged everyone like they do horses.