NEW CALENDAR XAML:

xaml = <StackPanel 
 xmlns = "http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
 xmlns:x = "http://schemas.microsoft.com/winfx/2006/xaml" 
 xmlns:controls = "clr-namespace:Microsoft.Windows.Controls;assembly=WPFToolkit" 
 xmlns:primitives = "clr-namespace:Microsoft.Windows.Controls.Primitives;assembly=WPFToolkit" 
 xmlns:vsm = "clr-namespace:System.Windows;assembly=WPFToolkit" 
 xmlns:src = "clr-namespace:GUI.UserInterface.ModuleControls.CalendarControl;assembly=planta">
 <StackPanel.Resources>
  <!--CalendarItem-->
  <Style x:Key = "calItemStyle" TargetType = "primitives:CalendarItem">
   <Setter Property = "Margin" Value = "0,3,0,3"/>
   <Setter Property = "Template">
    <Setter.Value>
     <ControlTemplate TargetType = "primitives:CalendarItem">
      <ControlTemplate.Resources>
       <!--Start: Data template for header button -->
       <DataTemplate x:Key = "DayTitleTemplate">
        <TextBlock FontWeight = "Bold" FontFamily = "Verdana" FontSize = "9.5" Foreground = "#FF333333" HorizontalAlignment = "Center" Text = "{Binding}" Margin = "0,6,0,6" VerticalAlignment = "Center"/>
       </DataTemplate>
       <!--End: Data template for header button -->
      </ControlTemplate.Resources>
      <Grid Name = "PART_Root">
       <Grid.Resources>
        <SolidColorBrush x:Key = "DisabledColor" Color = "#A5FFFFFF"/>
       </Grid.Resources>
       <vsm:VisualStateManager.VisualStateGroups>
        <vsm:VisualStateGroup x:Name = "CommonStates">
         <vsm:VisualState x:Name = "Normal"/>
         <vsm:VisualState x:Name = "Disabled">
          <Storyboard>
           <DoubleAnimation Storyboard.TargetName = "PART_DisabledVisual" Storyboard.TargetProperty = "Opacity" To = "1" Duration = "0"/>
          </Storyboard>
         </vsm:VisualState>
        </vsm:VisualStateGroup>
       </vsm:VisualStateManager.VisualStateGroups>
       <Border BorderBrush = "{TemplateBinding BorderBrush}" BorderThickness = "{TemplateBinding BorderThickness}" Background = "{TemplateBinding Background}" CornerRadius = "1">
        <Border CornerRadius = "1" BorderBrush = "#FFFFFFFF" BorderThickness = "2">
         <Grid>
          <Grid.RowDefinitions>
           <RowDefinition Height = "Auto"/>
           <RowDefinition Height = "*"/>
          </Grid.RowDefinitions>
          <Grid.ColumnDefinitions>
           <ColumnDefinition Width = "Auto"/>
           <ColumnDefinition Width = "Auto"/>
           <ColumnDefinition Width = "Auto"/>
          </Grid.ColumnDefinitions>
          <Grid.Resources>
           <!--Start: Previous button template -->
           <ControlTemplate x:Key = "PreviousButtonTemplate" TargetType = "Button">
            <Grid Cursor = "Hand">
             <vsm:VisualStateManager.VisualStateGroups>
              <vsm:VisualStateGroup x:Name = "CommonStates">
               <vsm:VisualState x:Name = "Normal"/>
               <vsm:VisualState x:Name = "MouseOver">
                <Storyboard>
                 <ColorAnimation Storyboard.TargetName = "TextColor" Storyboard.TargetProperty = "Color" To = "#FF73A9D8" Duration = "0"/>
                </Storyboard>
               </vsm:VisualState>
               <vsm:VisualState x:Name = "Disabled">
                <Storyboard>
                 <DoubleAnimation Storyboard.TargetName = "TextColor" Storyboard.TargetProperty = "Opacity" To = ".5" Duration = "0"/>
                </Storyboard>
               </vsm:VisualState>
              </vsm:VisualStateGroup>
             </vsm:VisualStateManager.VisualStateGroups>
             <Rectangle Fill = "#11E5EBF1" Stretch = "Fill" Opacity = "1"/>
             <Grid>
              <Path Margin = "14,-6,0,0" Height = "10" Width = "6" VerticalAlignment = "Center" HorizontalAlignment = "Left" Stretch = "Fill" Data = "M288.75,232.25 L288.75,240.625 L283,236.625 z">
               <Path.Fill>
                <SolidColorBrush x:Name = "TextColor" Color = "#FF333333"/>
               </Path.Fill>
              </Path>
             </Grid>
            </Grid>
           </ControlTemplate>
           <!--End: Previous button template -->
           <!--Start: Next button template -->
           <ControlTemplate x:Key = "NextButtonTemplate" TargetType = "Button">
            <Grid Cursor = "Hand">
             <vsm:VisualStateManager.VisualStateGroups>
              <vsm:VisualStateGroup x:Name = "CommonStates">
               <vsm:VisualState x:Name = "Normal"/>
               <vsm:VisualState x:Name = "MouseOver">
                <Storyboard>
                 <ColorAnimation Storyboard.TargetName = "TextColor" Storyboard.TargetProperty = "Color" To = "#FF73A9D8" Duration = "0"/>
                </Storyboard>
               </vsm:VisualState>
               <vsm:VisualState x:Name = "Disabled">
                <Storyboard>
                 <DoubleAnimation Storyboard.TargetName = "TextColor" Storyboard.TargetProperty = "Opacity" To = ".5" Duration = "0"/>
                </Storyboard>
               </vsm:VisualState>
              </vsm:VisualStateGroup>
             </vsm:VisualStateManager.VisualStateGroups>
             <Rectangle Fill = "#11E5EBF1" Stretch = "Fill" Opacity = "1"/>
             <Grid>
              <Path Margin = "0,-6,14,0" Height = "10" Width = "6" VerticalAlignment = "Center" HorizontalAlignment = "Right" Stretch = "Fill" Data = "M282.875,231.875 L282.875,240.375 L288.625,236 z">
               <Path.Fill>
                <SolidColorBrush x:Name = "TextColor" Color = "#FF333333"/>
               </Path.Fill>
              </Path>
             </Grid>
            </Grid>
           </ControlTemplate>
           <!--End: Next button template -->
           <!--Start: Header button template -->
           <ControlTemplate x:Key = "HeaderButtonTemplate" TargetType = "Button">
            <Grid Cursor = "Hand">
             <vsm:VisualStateManager.VisualStateGroups>
              <vsm:VisualStateGroup x:Name = "CommonStates">
               <vsm:VisualState x:Name = "Normal"/>
               <vsm:VisualState x:Name = "MouseOver">
                <Storyboard>
                 <ColorAnimation Storyboard.TargetName = "TextColor" Storyboard.TargetProperty = "Color" To = "#FF73A9D8" Duration = "0"/>
                </Storyboard>
               </vsm:VisualState>
               <vsm:VisualState x:Name = "Disabled">
                <Storyboard>
                 <DoubleAnimation Storyboard.TargetName = "buttonContent" Storyboard.TargetProperty = "Opacity" To = ".5" Duration = "0"/>
                </Storyboard>
               </vsm:VisualState>
              </vsm:VisualStateGroup>
             </vsm:VisualStateManager.VisualStateGroups>
             <ContentPresenter x:Name = "buttonContent" Content = "{TemplateBinding Content}" ContentTemplate = "{TemplateBinding ContentTemplate}" Margin = "1,4,1,9" HorizontalAlignment = "{TemplateBinding HorizontalContentAlignment}" VerticalAlignment = "{TemplateBinding VerticalContentAlignment}">
              <TextElement.Foreground>
               <SolidColorBrush x:Name = "TextColor" Color = "#FF333333"/>
              </TextElement.Foreground>
             </ContentPresenter>
            </Grid>
           </ControlTemplate>
           <!--End: Header button template -->
          </Grid.Resources>
          <!--Start: Previous button content -->
          <Button x:Name = "PART_PreviousButton" Grid.Row = "0" Grid.Column = "0" Template = "{StaticResource PreviousButtonTemplate}" Height = "20" Width = "28" HorizontalAlignment = "Left" Focusable = "False"/>
          <!--End: Previous button content -->
          <!--Start: Header button content -->
          <Button x:Name = "PART_HeaderButton" Grid.Row = "0" Grid.Column = "1" Template = "{StaticResource HeaderButtonTemplate}" HorizontalAlignment = "Center" VerticalAlignment = "Center" FontWeight = "Bold" FontSize = "10.5" Focusable = "False"/>
          <!--End: Header button content -->
          <!--Start: Next button content -->
          <Button x:Name = "PART_NextButton" Grid.Row = "0" Grid.Column = "2" Height = "20" Width = "28" HorizontalAlignment = "Right" Template = "{StaticResource NextButtonTemplate}" Focusable = "False"/>
          <!--End: Next button content -->
          <!--*************************************************************************** -->
          <!--New for WeekNumbers (Grid.Row & Grid.ColumnSpan lifted from PART_MonthView) -->
          <StackPanel Grid.Row = "1" Grid.ColumnSpan = "3" Grid.IsSharedSizeScope = "True" Margin = "6,-1,6,6" Orientation = "Horizontal">
           <Grid Visibility = "{Binding ElementName=PART_MonthView, Path=Visibility}" Background = "AliceBlue">
            <Grid.Resources>
             <Style TargetType = "TextBlock">
              <Setter Property = "FontFamily" Value = "Verdana"/>
              <Setter Property = "FontWeight" Value = "Bold"/>
              <Setter Property = "FontSize" Value = "9.5"/>
              <Setter Property = "Foreground" Value = "#FF333333"/>
              <Setter Property = "HorizontalAlignment" Value = "Center"/>
              <Setter Property = "VerticalAlignment" Value = "Center"/>
             </Style>
             <Style TargetType = "src:WeekNumber" BasedOn = "{StaticResource {x:Type TextBlock}}">
              <Setter Property = "FontWeight" Value = "Normal"/>
              <Setter Property = "FontSize" Value = "9.5"/>
             </Style>
            </Grid.Resources>
            <Grid.RowDefinitions>
             <RowDefinition Height = "Auto" SharedSizeGroup = "SharedTitleHeight"/>
             <RowDefinition Height = "Auto" SharedSizeGroup = "SharedItemHeight"/>
             <RowDefinition Height = "Auto" SharedSizeGroup = "SharedItemHeight"/>
             <RowDefinition Height = "Auto" SharedSizeGroup = "SharedItemHeight"/>
             <RowDefinition Height = "Auto" SharedSizeGroup = "SharedItemHeight"/>
             <RowDefinition Height = "Auto" SharedSizeGroup = "SharedItemHeight"/>
             <RowDefinition Height = "Auto" SharedSizeGroup = "SharedItemHeight"/>
            </Grid.RowDefinitions>
            <TextBlock Grid.Row = "0" Text = "CalendarWeekHeader"/>
            <src:WeekNumber Grid.Row = "1" Calendar = "{Binding RelativeSource={RelativeSource AncestorType=controls:Calendar}}"/>
            <src:WeekNumber Grid.Row = "2" Calendar = "{Binding RelativeSource={RelativeSource AncestorType=controls:Calendar}}"/>
            <src:WeekNumber Grid.Row = "3" Calendar = "{Binding RelativeSource={RelativeSource AncestorType=controls:Calendar}}"/>
            <src:WeekNumber Grid.Row = "4" Calendar = "{Binding RelativeSource={RelativeSource AncestorType=controls:Calendar}}"/>
            <src:WeekNumber Grid.Row = "5" Calendar = "{Binding RelativeSource={RelativeSource AncestorType=controls:Calendar}}"/>
            <src:WeekNumber Grid.Row = "6" Calendar = "{Binding RelativeSource={RelativeSource AncestorType=controls:Calendar}}"/>
           </Grid>
           <!--End of New for WeekNumbers                                                  -->
           <!--*************************************************************************** -->
           <!--Plus SharedSizeGroup added to next Grid                                     -->
           <!--Start: Month Content Grid -->
           <Grid x:Name = "PART_MonthView" Visibility = "Visible">
            <Grid.RowDefinitions>
             <RowDefinition Height = "Auto" SharedSizeGroup = "SharedTitleHeight"/>
             <RowDefinition Height = "Auto" SharedSizeGroup = "SharedItemHeight"/>
             <RowDefinition Height = "Auto" SharedSizeGroup = "SharedItemHeight"/>
             <RowDefinition Height = "Auto" SharedSizeGroup = "SharedItemHeight"/>
             <RowDefinition Height = "Auto" SharedSizeGroup = "SharedItemHeight"/>
             <RowDefinition Height = "Auto" SharedSizeGroup = "SharedItemHeight"/>
             <RowDefinition Height = "Auto" SharedSizeGroup = "SharedItemHeight"/>
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
             <ColumnDefinition Width = "Auto"/>
             <ColumnDefinition Width = "Auto"/>
             <ColumnDefinition Width = "Auto"/>
             <ColumnDefinition Width = "Auto"/>
             <ColumnDefinition Width = "Auto"/>
             <ColumnDefinition Width = "Auto"/>
             <ColumnDefinition Width = "Auto"/>
            </Grid.ColumnDefinitions>
           </Grid>
           <!--End: Month Content Grid -->
           <!--New for WeekNumbers -->
          </StackPanel>
          <!--End of new for WeekNumbers -->
          <!--End: Year Content Grid -->
          <Grid x:Name = "PART_YearView" Grid.Row = "1" Grid.ColumnSpan = "3" Visibility = "Hidden" Margin = "6,-3,7,6">
           <Grid.RowDefinitions>
            <RowDefinition Height = "Auto"/>
            <RowDefinition Height = "Auto"/>
            <RowDefinition Height = "Auto"/>
           </Grid.RowDefinitions>
           <Grid.ColumnDefinitions>
            <ColumnDefinition Width = "Auto"/>
            <ColumnDefinition Width = "Auto"/>
            <ColumnDefinition Width = "Auto"/>
            <ColumnDefinition Width = "Auto"/>
           </Grid.ColumnDefinitions>
          </Grid>
          <!--End: Year Content Grid -->
         </Grid>
        </Border>
       </Border>
       <Rectangle x:Name = "PART_DisabledVisual" Opacity = "0" Visibility = "Collapsed" Stretch = "Fill" StrokeThickness = "1" RadiusX = "2" RadiusY = "2" Stroke = "{StaticResource DisabledColor}" Fill = "{StaticResource DisabledColor}"/>
      </Grid>
      <ControlTemplate.Triggers>
       <Trigger Property = "IsEnabled" Value = "False">
        <Setter TargetName = "PART_DisabledVisual" Property = "Visibility" Value = "Visible"/>
       </Trigger>
       <DataTrigger Value = "Year">
        <DataTrigger.Binding>
         <Binding Path = "DisplayMode">
          <Binding.RelativeSource>
           <RelativeSource Mode = "FindAncestor" AncestorType = "{x:Type controls:Calendar}"/>
          </Binding.RelativeSource>
         </Binding>
        </DataTrigger.Binding>
        <Setter TargetName = "PART_MonthView" Property = "Visibility" Value = "Hidden"/>
        <Setter TargetName = "PART_YearView" Property = "Visibility" Value = "Visible"/>
       </DataTrigger>
       <DataTrigger Value = "Decade">
        <DataTrigger.Binding>
         <Binding Path = "DisplayMode">
          <Binding.RelativeSource>
           <RelativeSource Mode = "FindAncestor" AncestorType = "{x:Type controls:Calendar}"/>
          </Binding.RelativeSource>
         </Binding>
        </DataTrigger.Binding>
        <Setter TargetName = "PART_MonthView" Property = "Visibility" Value = "Hidden"/>
        <Setter TargetName = "PART_YearView" Property = "Visibility" Value = "Visible"/>
       </DataTrigger>
      </ControlTemplate.Triggers>
     </ControlTemplate>
    </Setter.Value>
   </Setter>
  </Style>
 </StackPanel.Resources>
 <controls:Calendar CalendarItemStyle = "{StaticResource calItemStyle}" Name = "Calendar" Margin = "0,-3,1,-2"/>
</StackPanel>