open modal segue with prepareForSegue method crashes app

I am opening a Modal view controller in my app, this modal view controller contains DatePicker.

The app's navigation hierarchy is

TabbarController->NavigationController->ViewController->ViewController

I have putted segue from first ViewController to second one and opening it in Modal segue.

I have putted Identifier to Modal segue, and connected the custom class too.

But when I write prepareForSegue method the app is crashes with following error.

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[DatePickerViewController viewControllers]: unrecognized selector sent to instance 0xa082360'

The code for prepareForSegue is

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.identifier isEqualToString:@"AddDate"])
    {
         UINavigationController *navigationController =segue.destinationViewController;

         DatePickerViewController *datePickerViewController =[[navigationController viewControllers] objectAtIndex:0];
         datePickerViewController.delegate = self;

    }
}

I have followed this tutorial for Modal segue http://www.raywenderlich.com/5191/beginning-storyboards-in-ios-5-part-2.

I think you connected your segue with view controller not with navigation controller. To fix this replace your code with:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.identifier isEqualToString:@"AddDate"])
    {
         DatePickerViewController *datePickerViewController = (DatePickerViewController*)segue.destinationViewController;
         datePickerViewController.delegate = self;

    }
}