lab/WpfApp1/MainWindow.xaml.cs

using System.Globalization;
using System.Windows.Data;
using System.Windows;

public class DateTimeToDateConverter : IValueConverter
{
    public object Convert(
        object value,
        Type targetType,
        object parameter,
        CultureInfo culture)
    {
        return ((DateTime)value).ToString("dd.MM.yyyy");
    }

    public object ConvertBack(
        object value,
        Type targetType,
        object parameter,
        CultureInfo culture)
    {
        return DependencyProperty.UnsetValue;
    }
}