@Override
  public int compareTo(TimestampTZ o) {
    return zonedDateTime.toInstant().compareTo(o.zonedDateTime.toInstant());
  }
Obtains an instance of Instant using seconds from the epoch of 1970-01-01T00:00:00Z and
nanosecond fraction of second. Then, it creates a zoned date-time with the same instant
as that specified but in the given time-zone.
common/src/java/org/apache/hadoop/hive/common/type/TimestampTZ.java