@Override
    public String toString() {
        StringBuilder buffer = new StringBuilder();
        if (hasDateStamp())
            buffer.append(getDateTime().toString());
        if (hasTimeStamp())
            buffer.append("@").append(String.format(Locale.US,"%.3f", getTimeStamp()));
        return buffer.toString();
    }
@Test
    void getDateStampAsString() {
        DateTimeStamp dateTimeStamp = new DateTimeStamp(.586);
        assertEquals("@0.586", dateTimeStamp.toString());

        dateTimeStamp = new DateTimeStamp("2018-04-04T09:10:00.586-0100");
        assertEquals("2018-04-04T09:10:00.586-01:00", dateTimeStamp.toString());

        dateTimeStamp = new DateTimeStamp("2018-04-04T09:10:00.586-0100", 0.18);
        assertEquals("2018-04-04T09:10:00.586-01:00@0.180", dateTimeStamp.toString());
    }