How to debug setter not firing on Timepicker property?

Question

Overview: I've added a Timepicker control to my UI and set the Time property binding to a DateTime property on the associated ViewModel.

But when I debug the solution the setter doesn't get called for the property SelectedParkDuration.

In order to debug this further I checked the data context for the UI. The data context is set correctly and the getter of the Timepicker is called.

Question: Does anyone know why the setter isn't getting called when I select a value on the time picker at runtime?

Time Picker control definition:

                   <TimePicker Grid.Row="2"
                    Grid.Column="1"
                    Width="270"
                    Height="100"
                    HorizontalAlignment="Center"
                    VerticalAlignment="Bottom"
                    Header="Parking Duration"
                    Time="{Binding SelectedParkDuration}"
                    />

Time picker property - SelectedParkDuration defined in the UI's ViewModel:

    private DateTime _selectedParkDuration;
    public DateTime SelectedParkDuration
    {
        get
        {
            return this._selectedParkDuration;
        }

        set
        {
            if (_selectedParkDuration != value)
            {
                _selectedParkDuration = value;
                RaisePropertyChanged("SelectedParkDuration");
            }
        }
    }

Answer 1

The solution is to specify two-way binding as @Ken Tucker suggested. Also the type of the property needed to be of type TimeSpan:

    private TimeSpan? _selectedParkDuration;
    public TimeSpan? SelectedParkDuration
    {
        get
        {
            return this._selectedParkDuration;
        }

        set
        {
            if (_selectedParkDuration != value)
            {
                _selectedParkDuration = value;
                RaisePropertyChanged("SelectedParkDuration");
            }
        }
    }

Xaml definition of TimePicker:

<TimePicker Grid.Row="2"
                        Grid.Column="1"
                        Width="270"
                        Height="100"
                        HorizontalAlignment="Center"
                        VerticalAlignment="Bottom"
                        Header="Parking Duration"
                        Time="{Binding SelectedParkDuration,
                                       Mode=TwoWay}" />