Nintendo's upcoming account system, Nintendo Account, will allow users to receive special birthday discounts as long as a few conditions are met. If a user links his/her Nintendo Network ID with the account before the 24th day of their respective birthday month and choose to receive promotional e-mails from Nintendo, Nintendo will send the user special discount codes as a birthday present. For example, if you were born in the month of October, you would need to register with Nintendo Account before October 24th so that Nintendo can send you an e-mail on the 24th with discount codes.
At the moment, these discount codes are only available in Japan. Once Nintendo Account launches in other regions, it is likely that these promotions may be available, but for now, there is no further information regarding these features. However, it should not take long before Nintendo announces more information about Nintendo Account for North America and Europe.