Method between

base/src/main/java/net/time4j/SI.java:95–133

(
        Moment start,
        Moment end
    )

     * @throws  UnsupportedOperationException wenn ein Zeitpunkt vor 1972 ist
     */
    public long between(
        Moment start,
        Moment end
    ) {

        Moment.check1972(start);
        Moment.check1972(end);

        switch (this) {
            case SECONDS:
                long delta = (
                    end.getElapsedTime(TimeScale.UTC)
                    - start.getElapsedTime(TimeScale.UTC));
                if (delta < 0) {
                    if (end.getNanosecond() > start.getNanosecond()) {
                        delta++;
                    }
                } else if (delta > 0) {
                    if (end.getNanosecond() < start.getNanosecond()) {
                        delta--;
                    }
                }
                return delta;
            case NANOSECONDS:
                return MathUtils.safeAdd(
                    MathUtils.safeMultiply(
                        MathUtils.safeSubtract(
                            end.getElapsedTime(TimeScale.UTC),
                            start.getElapsedTime(TimeScale.UTC)
                        ),
                        1000000000
                    ),
                    end.getNanosecond() - start.getNanosecond()
                 );
            default:
                throw new UnsupportedOperationException();
        }

    }

    @Override
    public double getLength() {