3rdpartylibs/fastreports.wpf/FastReport.Forms.WPF/CustomControls/Calendar.xaml

<Calendar x:Class="CustomControls.Calendar"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:CustomControls">
    <Calendar.Resources>
        <local:LookupDatesConverter x:Key="HighlightDate" />
        <local:LookupAnnualDatesConverter x:Key="HighlightAnnualDate" />
        <local:LookupMonthDatesConverter x:Key="HighlightMonthDate" />
    </Calendar.Resources>
    <Calendar.CalendarDayButtonStyle>
        <Style TargetType="CalendarDayButton">
            <Setter Property="FontFamily" Value="{Binding FontFamily, RelativeSource={RelativeSource AncestorType={x:Type local:Calendar}}}" />
            <Setter Property="FontSize" Value="{Binding FontSize, RelativeSource={RelativeSource AncestorType={x:Type local:Calendar}}}" />
            <Setter Property="FontWeight" Value="{Binding FontWeight, RelativeSource={RelativeSource AncestorType={x:Type local:Calendar}}}" />
            <Style.Triggers>
                <DataTrigger Value="True">
                    <DataTrigger.Binding>
                        <MultiBinding Converter="{StaticResource HighlightDate}">
                            <Binding />
                            <Binding Path="DataContext.Dates" RelativeSource="{RelativeSource AncestorType={x:Type local:Calendar}}" />
                        </MultiBinding>
                    </DataTrigger.Binding>
                    <Setter Property="FontWeight" Value="Bold" />
                </DataTrigger>

                <DataTrigger Value="True">
                    <DataTrigger.Binding>
                        <MultiBinding Converter="{StaticResource HighlightAnnualDate}">
                            <Binding />
                            <Binding Path="DataContext.AnnualDates" RelativeSource="{RelativeSource AncestorType={x:Type local:Calendar}}" />
                        </MultiBinding>
                    </DataTrigger.Binding>
                    <Setter Property="FontWeight" Value="Bold" />
                </DataTrigger>

                <DataTrigger Value="True">
                    <DataTrigger.Binding>
                        <MultiBinding Converter="{StaticResource HighlightMonthDate}">
                            <Binding />
                            <Binding Path="DataContext.MonthDates" RelativeSource="{RelativeSource AncestorType={x:Type local:Calendar}}" />
                        </MultiBinding>
                    </DataTrigger.Binding>
                    <Setter Property="FontWeight" Value="Bold" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </Calendar.CalendarDayButtonStyle>
</Calendar>