docs: public void setInterval(ReadableInstant start, ReadableInstant end) {
          if (start == null && end == null) {
              long now = DateTimeUtils.currentTimeMillis();
              setInterval(now, now);
          } else {
              long startMillis = DateTimeUtils.getInstantMillis(start);
              long endMillis = DateTimeUtils.getInstantMillis(end);
              Chronology chrono = DateTimeUtils.getInstantChronology(start);
              super.setInterval(startMillis, endMillis, chrono);
          }
      }