Check EKEvent out
EKEventStore *eventDB = [[EKEventStore alloc] init];
EKEvent *myEvent  = [EKEvent eventWithEventStore:eventDB];
myEvent.title     = @"New Event";
myEvent.startDate = [[NSDate alloc]init ];
myEvent.endDate   = [[NSDate alloc]init ];
myEvent.allDay = YES;
[myEvent setCalendar:[eventDB defaultCalendarForNewEvents]];
NSError *err;
[eventDB saveEvent:myEvent span:EKSpanThisEvent error:&err]; 
    UIAlertView *alert = [[UIAlertView alloc]
                          initWithTitle:@"Event Created"
                          message:@"Yay!?"
                          delegate:nil
                          cancelButtonTitle:@"Okay"
                          otherButtonTitles:nil];
    [alert show];