Looks like there's a default calendar called Birthdays in Calendar and it's driven off of a birthday's field in Contacts. I want to share this calendar but hovering over it in Calendar it doesn't give me the option (unlike all the other calendars). If Contacts are shared through iCloud I assume that the Birthday field is shared too. If so, is it also sharing the Birthday calendar even though it won't let me share it through the Calendar application? A related afterthought question...could I create new fields in Contacts such as "Anniversary" and drive a calendar off of it as well in the same way Birthday does?