When you add the linkedin app on your iphone it is dutifully populated by iphone calendar with everyone’s birthday which when interested is nice but when you are challenged for screen estate on the iphone, it becomes a problem. Honestly even though it is nice to send people birthday gifts and cards, it is not going to happen to all people in my contacts, so it turns out to be a nuisance.
You can easily remove this by tapping on Calendar settings, look for “other” and uncheck birthdays. Finally they are gone…no more nuisance.