Of course I know my birthdate (and year!).
I just don't choose to share it.
-- but everyone appears to have settled on me being Sagittarius. Or Capricorn. Or something.
Actually, the best guess puts your birthday somewhere in late July - which could make you a.... Oh dear.
PS: This is a cracking good book.
That book old son, is right up my street.
Duly added to the Christmas list (although I might not get it until next July now).