code: public PeriodDuration normalizedStandardDays() {
          long totalSecs = period.getDays() * SECONDS_PER_DAY + duration.getSeconds();
          int splitDays = Math.toIntExact(totalSecs / SECONDS_PER_DAY);
          long splitSecs = totalSecs % SECONDS_PER_DAY;
          if (splitDays == period.getDays() && splitSecs == duration.getSeconds()) {
              return this;
          }
          return PeriodDuration.of(period.withDays(splitDays), duration.withSeconds(splitSecs));
      }
docs: Returns a copy of this instance with the days and duration normalized using the standard day of 24 hours.
  <p>
  This normalizes the days and duration, leaving the years and months unchanged.
  The result uses a standard day length of 24 hours.
  <p>
  This combines the duration seconds with the number of days and shares the total
  seconds between the two fields. For example, a period of
  "2 days and 86401 seconds" will be normalized to "3 days and 1 second".
  <p>
  The sign of the days and duration will be the same after normalization.
  For example, a period of "1 day and -172801 seconds" will be normalized to
  "-1 day and -1 second".
  <p>
  Note that no normalization is performed on the years or months.
  <p>
  This instance is immutable and unaffected by this method call.
  
  @return a {@code PeriodDuration} based on this one with excess duration normalized to days, not null
  @throws ArithmeticException if numeric overflow occurs