Is there something extra to be done in WPF to show a DataGrid of only DateTime objects?

XAML:

 <DataGrid
    ItemsSource="{Binding Path=Model.Dates}"
    AutoGenerateColumns="False"
    CanUserAddRows="True"
    CanUserDeleteRows="True"
    CanUserSortColumns="True"
    CanUserReorderColumns="True"
    AlternatingRowBackground="WhiteSmoke"
    SelectionUnit="Cell">

 <DataGrid.Columns>
     <DataGridTextColumn Header="Date" Binding="{Binding Path=., Converter={StaticResource dateConverter}}" />
 </DataGrid.Columns>

Model:

    private ObservableCollection<DateTime> _dates= new 
    ObservableCollection<DateTime>() { DateTime.Today };

    public ObservableCollection<DateTime> Dates
{
    get { return _dates; }
    set
    {
        _dates= value;
        OnPropertyChanged("Dates");
    }
}

DateConverter is a simple converter which formats the dates into a custom format.

Yet, this simple set-up doesn’t allow me to add new rows and returns an error on editing (Two-way path not setup).

Wrapping the dates in a custom object:

 public class TestData
 {
     public DateTime Date{ get; set; }
 }

And setting the Dates in the model as:

    private ObservableCollection<TestData> _dates = new ObservableCollection<TestData>();

Change in XAML of the Column:

<DataGrid.Columns>
         <DataGridTextColumn Header="Date" Binding="{Binding Path=Date, Converter={StaticResource dateConverter}}" />
     </DataGrid.Columns>

Does give a correctly working DataGrid which allows to add new rows and edit existing cells.