Is there any way in WP8 to easily get the birthdays and anniversaries you've entered in the people hub into the calendar app without having to type them in again?
I am on WP 7, but this should be only incidental. If it is an option, you could synchronise your contacts to your LIVE account and create an outlook.com-Account (you don't have to use it for e-mail). There you should get an birthday-calendar for your contacts automatically. It should also sync with your contacts, whenever you edit or add a new contact.
You can import this calendar by synchronizing your phone with the outlook account. Then you can enable it from the Settings-menu in the calendar hub.
Hope this helps!