
**Apache Airflow version**:

master

**What happened**:

https://github.com/apache/airflow/blob/master/airflow/models/baseoperator.py#L356 --> should be timedelta not datetime


airflow/serialization/serialized_objects.py
value = getattr(op, template_field, None)
                if not cls._is_excluded(value, template_field, op):
                    serialize_op[template_field] = serialize_template_field(value)
        return serialize_op
    @classmethod
    def deserialize_operator(cls, encoded_op: Dict[str, Any]) -> BaseOperator:
        """Deserializes an operator from a JSON object."""
        op = SerializedBaseOperator(task_id=encoded_op['task_id'])
        if "label" not in encoded_op:
            
            encoded_op["label"] = encoded_op["task_id"]
        
        op_extra_links_from_plugin = {}
        
        if cls._load_operator_extra_links:  
            from airflow import plugins_manager
            plugins_manager.initialize_extra_operators_links_plugins()
            if plugins_manager.operator_extra_links is None:
                raise AirflowException("Can not load plugins")
            for ope in plugins_manager.operator_extra_links:
                for operator in ope.operators:
                    if (
                        operator.__name__ == encoded_op["_task_type"]
                        and operator.__module__ == encoded_op["_task_module"]
                    ):
                        op_extra_links_from_plugin.update({ope.name: ope})