iOS 9 swift 2 ekeventviewcontroller 에서 done 버튼이 나타나지 않을 때

func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
        let eventVC = EKEventViewController()
        eventVC.event = eventItems[indexPath.row]
        eventVC.allowsEditing = true
        eventVC.allowsCalendarPreview = true
        eventVC.delegate = self
        self.presentViewController(eventVC, animated: true, completion: nil)
}

위와 같이 했는데 Done 버튼이 나타나지 않음

아래와 같이 네이게이션 컨트롤러를 추가하고 모달 스타일을 페이지 시트로 변경하니 잘 나옴

func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
    let eventVC = EKEventViewController()
    eventVC.event = eventItems[indexPath.row]
    eventVC.allowsEditing = true
    eventVC.allowsCalendarPreview = true
    eventVC.delegate = self

    let nav = UINavigationController(rootViewController: eventVC)
    nav.modalPresentationStyle = .PageSheet
    self.presentViewController(nav, animated: true, completion: nil)
}