public static void updateTimestamp(Timestamp timestamp, long secondsAsMillis, int nanos) {
    ((Date) timestamp).setTime(secondsAsMillis);
    timestamp.setNanos(nanos);
  }
true if data is stored in timestamp field rather than byte arrays.
     allows for lazy conversion to bytes when necessary
false otherwise
serde/src/java/org/apache/hadoop/hive/serde2/io/TimestampWritable.java