//xaml
<Window x:Class="WpfApp427.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApp427"
mc:Ignorable="d"
WindowState="Maximized"
Title="MainWindow" Height="450" Width="800">
<Window.Resources>
<Style TargetType="Calendar">
<Setter Property="IsTodayHighlighted" Value="True"/>
</Style>
</Window.Resources>
<Grid>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<Calendar Grid.Row="0" Grid.Column="0" DisplayMode="Month" SelectionMode="SingleDate" FirstDayOfWeek="Monday"/>
<Calendar Grid.Row="0" Grid.Column="1" DisplayMode="Year" SelectionMode="SingleRange" FirstDayOfWeek="Sunday" />
<Calendar Grid.Row="0" Grid.Column="2" DisplayMode="Decade" SelectionMode="MultipleRange" FirstDayOfWeek="Saturday"/>
<Calendar Grid.Row="1" Grid.Column="0">
<Calendar.BlackoutDates>
<CalendarDateRange Start="9/1/2024" End="9/5/2024"/>
<CalendarDateRange Start="9/10/2024" End="9/15/2024"/>
<CalendarDateRange Start="9/20/2024" End="9/25/2024"/>
</Calendar.BlackoutDates>
</Calendar>
</Grid>
</Window>