@Override
  public void setTimestamp(byte[] ts) {
    Bytes.putBytes(this.bytes, this.getTimestampOffset(), ts, 0, Bytes.SIZEOF_LONG);
  }
Update the timestamp.
@param now Time to set into <code>this</code> IFF timestamp ==
           {@link HConstants#LATEST_TIMESTAMP} (else, its a noop).
@return True is we modified this.
hbase-common/src/main/java/org/apache/hadoop/hbase/KeyValue.java