<sg:CalendarDayButtonStyleSelector x:Key="StyleSelector">
    <sg:CalendarDayButtonStyleSelector.Conditions>
        <sg:DayOfWeekCondition DayOfWeek="Wednesday">
            <sg:DayOfWeekCondition.Setters>
                <sg:SelectorSetter Property="FontSize" Value="20"/>
            </sg:DayOfWeekCondition.Setters>
        </sg:DayOfWeekCondition>
        <sg:PropertyCondition Property="IsHoliday" Value="true">
            <sg:PropertyCondition.Setters>
                <sg:SelectorSetter Property="Foreground" Value="Red"/>
            </sg:PropertyCondition.Setters>
        </sg:PropertyCondition>
    </sg:CalendarDayButtonStyleSelector.Conditions>
</sg:CalendarDayButtonStyleSelector>
<Style TargetType="sg:DropDownCalendarEditElement">
    <Setter Property="HolidaySetting">
        <Setter.Value>
            <sg:HolidaySetting IsActive="True">
                <sg:DayOfWeekHoliday DayOfWeek="Wednesday" Month="All" WeekInMonth="All" />
            </sg:HolidaySetting>
        </Setter.Value>
    </Setter>
    <Setter Property="CalendarDayButtonStyleSelector">
        <Setter.Value>
            <StaticResource ResourceKey="StyleSelector"/>
        </Setter.Value>
    </Setter>
</Style>