With games on consoles, it takes your birthday from your account. Whereas in Gems of War, there isn’t anywhere currently where we ask you for information like that.
In future, maybe we could add something but not sure how many people would appreciate putting in their birth date. An alternative could be a game anniversary, and then you get a mail for it. But would involve client work to recognise your yearly anniversary, and then trigger something being sent out - which is not possible currently.