fixed #398

src/Shared/HandyControl_Shared/Themes/Styles/Calendar.xaml

@@ -226,6 +226,7 @@
                                 </Grid>
                             </Border>
                         </Border>
+                        <Rectangle x:Name="PART_DisabledVisual" Visibility="Collapsed"/>
                     </hc:SimplePanel>
                     <ControlTemplate.Triggers>
                         <DataTrigger Binding="{Binding DisplayMode, RelativeSource={RelativeSource  AncestorType=Calendar}}" Value="Year">