Realize this is an older thread but I recently started trying to integrate my outlook calendar with various Icloud devices and mysteriously got a bunch (maybe 100 or so) alerts about birthdays coming up tomorrow, Jan 1st. Seems if a birthday is entered in the Outlook contacts, it automatically enters it in the calendar. Can't be disabled. In checking the alerted contacts, they do in fact, have Jan 1, 1900 entered as a birthday so I have to go thru and delete that birthday entry in all the affected contacts. Don't have a clue how those birthday entries got made but if anyone can advise, it would be appreciated.