ExtendedDatePickerRenderer.cs

using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
...

[assembly: ExportRenderer(typeof(ExtendedDatePicker), typeof(ExtendedDatePickerRenderer))]
...

public class ExtendedDatePickerRenderer : DatePickerRenderer
{
    public ExtendedDatePickerRenderer(Context context) : base(context)
    {
    }

    protected override void OnElementChanged(ElementChangedEventArgs<DatePicker> e)
    {
        base.OnElementChanged(e);

        Control.CustomSelectionActionModeCallback = new CustomSelectionActionModeCallback();
        Control.CustomInsertionActionModeCallback = new CustomInsertionActionModeCallback();
    }
}