code: public Duration durationUntil(UtcInstant utcInstant) {
          TaiInstant thisTAI = toTaiInstant();
          TaiInstant otherTAI = utcInstant.toTaiInstant();
          return thisTAI.durationUntil(otherTAI);
      }
docs: Returns the duration between this instant and the specified instant.
  <p>
  This calculates the duration between this instant and another based on
  the UTC time-scale. Any leap seconds that occur will be included in the duration.
  Adding the duration to this instant using {@link #plus} will always result
  in an instant equal to the specified instant.
  
  @param utcInstant  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