First, the output ("2025-06-22 10:02:48", "2025-06-22 10:02:48") of serialized DatePair is not a standard JSON, that mean's you can not using SerializerProvider.defaultSerializeValue . You need create a format with JsonFormator define a default, and the Serializer (recommended extends StdSerializer) should implements ContextualSerializer. You can refer to the implementation of DateSerializer and DateTimeSerializerBase.