code: public void setOccurrences(String occurrences) {
  
          int o = CmsSerialDateUtil.toIntWithDefault(occurrences, -1);
          if (m_model.getOccurrences() != o) {
              m_model.setOccurrences(o);
              valueChanged();
          }
      }
docs: Set the occurrences. If the String is invalid, the occurrences will be set to "-1" to cause server-side validation to fail.
  @param occurrences the interval to set.