Items are put on the calendar by creating a "content" item called an "event."  You will see that you can set them to "repeat" on an annual basis in which case you do not have to add them next year.  However, I have found that once you set an event to "repeat," you cannot edit it anymore.  This is a defect which hopefully will be fixed soon, but try to make sure you put them in the way you want them the first time.  It is a pain to have to put them in again.  I would suggest that you start by putting them in without the repeat function and then edit them to repeat when you are sure you have them the way you want them.  Also, please try to standardize the way all birthdays and other similar holidays are input so they all look the same (except for names and dates obviously) .