public void Main()
{
CultureInfo.CurrentCulture = new CultureInfo("de-DE");
var today = DateTime.Today;
WriteLine($"heute ist: {today:D}");
FormattableString s = $"heute ist: {today:d} und {today:D}";
WriteLine(FormattableString.Invariant($"heute ist: {today:d}"));
WriteLine(s.Spanish());
s.DisplayString();
}