docs: private long getCombinedValue(UTCDateBox date, UTCTimeBox time) {
          Long dateValue = date.getValue();
          Long timeValue = time.getValue();
      
          if (dateValue != null) {
              if (timeValue != null) {
                  return dateValue + timeValue;
              }
              else {
                  return dateValue;
              }
          }
          else {
              if (timeValue != null) {
                  return timeValue;
              }
              else {
                  return 0;
              }
          }
      }