
**Apache Airflow version**:

master

**What happened**:

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


airflow/models/baseoperator.py
params: Optional[Dict] = None,
        default_args: Optional[Dict] = None,  
        priority_weight: int = 1,
        weight_rule: str = WeightRule.DOWNSTREAM,
        queue: str = conf.get('celery', 'default_queue'),
        pool: Optional[str] = None,
        pool_slots: int = 1,
        sla: Optional[timedelta] = None,
        execution_timeout: Optional[timedelta] = None,
        on_execute_callback: Optional[TaskStateChangeCallback] = None,
        on_failure_callback: Optional[TaskStateChangeCallback] = None,
        on_success_callback: Optional[TaskStateChangeCallback] = None,
        on_retry_callback: Optional[TaskStateChangeCallback] = None,
        trigger_rule: str = TriggerRule.ALL_SUCCESS,
        resources: Optional[Dict] = None,
        run_as_user: Optional[str] = None,
        task_concurrency: Optional[int] = None,
        executor_config: Optional[Dict] = None,
        do_xcom_push: bool = True,
        inlets: Optional[Any] = None,
        outlets: Optional[Any] = None,
        task_group: Optional["TaskGroup"] = None,
        **kwargs,
    ):
        from airflow.models.dag import DagContext
        from airflow.utils.task_group import TaskGroupContext
        super().__init__()
        if kwargs:
            if not conf.getboolean('operators', 'ALLOW_ILLEGAL_ARGUMENTS'):
                raise AirflowException(