docs: public static final Chronology getIntervalChronology(ReadableInstant start, ReadableInstant end) {
          Chronology chrono = null;
          if (start != null) {
              chrono = start.getChronology();
          } else if (end != null) {
              chrono = end.getChronology();
          }
          if (chrono == null) {
              chrono = ISOChronology.getInstance();
          }
          return chrono;
      }