public void set(byte[] bytes, int offset, ZoneId timeZone) {
    externalBytes = bytes;
    this.offset = offset;
    this.timeZone = timeZone;
    bytesEmpty = false;
    timestampTZEmpty = true;
    currentBytes = externalBytes;
  }
true if data is stored in timestamptz field rather than byte arrays.
allows for lazy conversion to bytes when necessary
false otherwise
serde/src/java/org/apache/hadoop/hive/serde2/io/TimestampLocalTZWritable.java