I had my calendar duplicate on my mac and on my iphone.. on my mac I just deleted all my on my mac calendars and left the ones that are on the icloud. That got my mac ical working well with no duplicates..on my icloud also I have no duplicates but on my iphone even after turning the icloud calendar on and off which then lets you delete the calendars on the iphone I still get my calendar in the notification center with the things I have to do and if I click on the ical app I have NOTHING. If I go back and turn the icloud calendar sync on which should replace everything then I get duplicates of each event on the notification center and on my ical app my calendars and events now appear properly. Tried restoring it. Played around with the syncing options. Tried deleting my calendars on my iphone but couldn't. Tried all night yesterday. Any suggestion would help thanks.