How to change the display text of the WinUI Calendar (SfCalendar) dates

<Window
    x:Class="Custom_LeadTrailDates.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:Custom_LeadTrailDates"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    xmlns:calendar="using:Syncfusion.UI.Xaml.Calendar">
    
    <calendar:SfCalendar x:Name="calendar"
                        CornerRadius="14"
                        DayOfWeekFormat="{}{dayofweek.abbreviated(3)}">
    </calendar:SfCalendar>
</Window>

public sealed partial class MainWindow : Window
{
    public MainWindow()
    {
        this.InitializeComponent();
        calendar.ItemPrepared += Calendar_ItemPrepared;
    }
    private void Calendar_ItemPrepared(object sender, Syncfusion.UI.Xaml.Calendar.CalendarItemPreparedEventArgs e)
    {
        if (e.ItemInfo.DateInfo.HasFlag(Syncfusion.UI.Xaml.Calendar.CalendarDateInfo.OutOfScope))
        {
            e.ItemInfo.DisplayText = "x";
        }
    }
}