Wie wird alle zwei Wochen eine lokale Benachrichtigung ausgelöst?

Was ich getan habe war:

UILocalNotification *localNotification = UILocalNotification.new;
localNotification.repeatInterval = 14;
localNotification.fireDate = [NSDate dateWithTimeInterval:10 sinceDate:notificationDate];
localNotification.alertBody = notificationMessage;
localNotification.alertAction = @"Open";
localNotification.category = @"default_category";
[[UIApplication sharedApplication] scheduleLocalNotification:localNotification];