Cannot set date on UIDatePicker

I have a DatePickerView in my application (using UINavigationViewController) which I use to select date (UIDatePickerModeDate). Below is desired behavior

1. When user makes a selection I save the value in NSDate member variable so that I can set that value when needed.
2. Once the user makes a selection he can move to next view. If the user comes back to datepicker view then UIDatePicker should show previous selection.

Now I am testing following situation

1. User makes a selection (lets say Feb 21,2017) which sets a value to my member variable selectedDate.
2. Now he spins the year wheel and while its spinning move to next screen/view.
3. When user navigates back to DatePicker view, I set the UIDatePicker date to Feb 21, 2017 (in viewWillAppear) which is previous selection but I see a different value. It seems that I am seeing the value that would appear if I would have waited until the wheel would have stop spinning in step 2.

I don't know what am I missing. All I want is to set a value on UIDatePicker and looks like there is not way I can do that. Any help is appreciated. Thanks

Here is code

- (void)viewDidLoad {
    [super viewDidLoad];
    [self.datePicker addTarget:self action:@selector(onWheelSpin) forControlEvents:UIControlEventValueChanged];
}
-(void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    if(self.selectedDate) {
        NSLog(@"Setting date to %@",self.selectedDate.description);
        [self.datePicker setDate:self.selectedDate];
    } else {
        [self.datePicker setDate:[NSDate date]];
    }
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}
- (void) onWheelSpin {
    NSLog(@"Date Picker has been rolled.");
    [self setSelectedDate:[self.datePicker date]];
    NSLog(@"Selected date = %@",self.datePicker.date.description);
}