Set the Default Date of WPF Date Picker to Current Date

I have a WPF Datagrid in which one of the columns is a Date Column.

So i have used a DataTemplateColumn as Follows

<my:DataGridTemplateColumn
    CellTemplate="{StaticResource EffDateDateTimePickerControl}"
    CellEditingTemplate="{StaticResource addrEffDate}"
    Header="Effective Date"/>

And in my Resource File i have written the following code:

<Style TargetType="{x:Type my:Calendar}" x:Key="CalenderControlTemplate">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="my:Calendar" >
                <my:CalendarItem Name="myCalendarItem" 
                                 Background="White" 
                                 BorderBrush="Black"
                                 BorderThickness="1"
                                 VerticalAlignment="Center" />
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style> 

<DataTemplate x:Key="EffDateDateTimePickerControl">
    <Label x:Name="lblEffDate" Content="{Binding effectiveDate,Mode=TwoWay}" ></Label>
</DataTemplate>

<DataTemplate x:Key="addrEffDate">
    <my:DatePicker x:Name="dpEffDate" Text="{Binding Path=effectiveDate,Mode=TwoWay}"
                   SelectedDate="{Binding Now}" DisplayDateStart="{Binding Now}"
                   CalendarStyle="{DynamicResource CalenderControlTemplate}" />
</DataTemplate>

The problem is when i click on the DatePicker control the default date is set to 1/1/0001?

How can i set my datepicker to set to the current Date.