@Override
  public void stringifyValue(StringBuilder buffer, int row) {
    if (isRepeating) {
      row = 0;
    }
    if (noNulls || !isNull[row]) {
      scratchTimestamp.setTime(time[row]);
      scratchTimestamp.setNanos(nanos[row]);
      if (isUTC) {
        LocalDateTime ts =
            LocalDateTime.ofInstant(Instant.ofEpochMilli(time[row]), ZoneOffset.UTC).withNano(nanos[row]);
        buffer.append(ts.toLocalDate().toString() + ' ' + ts.toLocalTime().toString());
      } else {
        buffer.append(scratchTimestamp.toString());
      }
    } else {
      buffer.append("null");
    }
  }
Set the utc boolean variable
@param value
storage-api/src/java/org/apache/hadoop/hive/ql/exec/vector/TimestampColumnVector.java