code: private BigDecimal getLongitudeHour(Calendar date, Boolean isSunrise) {
          int offset = 18;
          if (isSunrise) {
              offset = 6;
          }
          BigDecimal dividend = BigDecimal.valueOf(offset).subtract(getBaseLongitudeHour());
          BigDecimal addend = divideBy(dividend, BigDecimal.valueOf(24));
          BigDecimal longHour = getDayOfYear(date).add(addend);
          return setScale(longHour);
      }
docs: Computes the longitude time, t in the algorithm.
  
  @return longitudinal time in <code>BigDecimal</code> form.