
**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
self.__dict__ = state  
        self._log = logging.getLogger("airflow.task.operators")
    def render_template_fields(self, context: Dict, jinja_env: Optional[jinja2.Environment] = None) -> None:
        """
        Template all attributes listed in template_fields. Note this operation is irreversible.
        :param context: Dict with values to apply on content
        :type context: dict
        :param jinja_env: Jinja environment
        :type jinja_env: jinja2.Environment
        """
        if not jinja_env:
            jinja_env = self.get_template_env()
        self._do_render_template_fields(self, self.template_fields, context, jinja_env, set())
    def _do_render_template_fields(
        self,
        parent: Any,
        template_fields: Iterable[str],
        context: Dict,
        jinja_env: jinja2.Environment,
        seen_oids: Set,
    ) -> None:
        for attr_name in template_fields:
            content = getattr(parent, attr_name)
            if content:
                rendered_content = self.render_template(content, context, jinja_env, seen_oids)
                setattr(parent, attr_name, rendered_content)
    def render_template(