public void Roundtrip2()
{
DateTime tmp = DateTime.UtcNow;
DateTimeOffset now = new DateTime(tmp.Year, tmp.Month, tmp.Day, tmp.Hour, tmp.Minute, tmp.Second, DateTimeKind.Utc);
var conv = new DateTimeOffsetConverter("R");
string?tmp1 = conv.ConvertToString(now);
Assert.IsNotNull(tmp1);
var now2 = (DateTimeOffset?)conv.Parse(tmp1);
Assert.AreEqual(now, now2);
}