Dowser.Elasticsearch.Codec.Date (Dowser.Elasticsearch v0.4.1)

date — ISO-8601 strings or epoch millis <-> DateTime.

A mapping entry with no "format" is treated as Elasticsearch's own default, strict_date_optional_time||epoch_millis. Custom Java date formats aren't parsed; unrecognized strings pass through untouched (write your own codec over these types to handle them).