You can use mind deposit to store birthdays. Just make a book, call it Birthdays, in the text field write the name and the birthday of the person. Set the reminder to remind you on the date that you prefer. You may want to be reminded a week before if you want to get a gift, a couple days before if you want to set a lunch or on the exact day if you plan to just call. In the drop down list, choose to be reminded on a yearly basis.