`org.logstash.Timestamp` Seems Redundant?

`org.logstash.Timestamp` holds no state beyond the `org.joda.time.DateTime` it wraps.
It seems the only point of having it around is to format timestamps a certain way and facilitate serialization via `org.logstash.json.TimestampSerializer`?

Both the formatting of the timestamp as well as the serialization in a certain format can be achieved by other (faster and 0GC) means from a `long`.
Is there any reason to keep this class around and not replace it with a less heavy approach?

(same goes for related logic around `org.logstash.ext.JrubyTimestampExtLibrary` and the `BiValue` we have for this one)