code: static double getValue(
          Moment moment,
          TimeScale scale
      ) {
  
          long elapsedTime = moment.getElapsedTime(scale) + jdOffset(scale);
          int nano = moment.getNanosecond(scale);
          double secs = elapsedTime + nano / (MRD * 1.0);
          return secs / DAY_IN_SECONDS;
  
      }
docs: obtains the JD-value for given moment and scale