code: public Duration durationUntil(TaiInstant otherInstant) {
          long durSecs = Math.subtractExact(otherInstant.seconds, seconds);
          long durNanos = otherInstant.nanos - nanos;
          return Duration.ofSeconds(durSecs, durNanos);
      }
docs: Returns the duration between this instant and the specified instant.
  <p>
  This calculates the duration between this instant and another based on
  the TAI time-scale. Adding the duration to this instant using {@link #plus}
  will always result in an instant equal to the specified instant.
  
  @param otherInstant  the instant to calculate the duration until, not null
  @return the duration until the specified instant, may be negative, not null
  @throws ArithmeticException if the calculation exceeds the supported range