Getting airflow exception: DAG is missing start_date parameter

When I checked the documentation, it was not mentioned anywhere that the start_date is a required parameter to be passed while creating a dag. I am getting the following error when I don't pass the parameter:

Broken DAG: [/opt/airflow/dags/dag_api_to_minio.py] Traceback (most recent call last):
File "/home/airflow/.local/lib/python3.7/site-packages/airflow/models/baseoperator.py", line 1039, in dag
dag.add_task(self)
File "/home/airflow/.local/lib/python3.7/site-packages/airflow/models/dag.py", line 2328, in add_task
raise AirflowException("DAG is missing the start_date parameter")
airflow.exceptions.AirflowException: DAG is missing the start_date parameter

Here is my dag definition using the TaskFlow API:

@dag(start_date=None,
schedule_interval=None, 
max_active_runs=1,
catchup=False,
default_args={
    "retries": 1,
    "retry_delay": timedelta(minutes=3)
},)

Versions: airflow:2.5.1, python:3.7
Can someone please explain what is going in here?

Expected output: The code should run without any errors as start_date is not a required parameter
Actual output: airflow exception: missing start_date parameter

> it was not mentioned anywhere that the start_date is a required parameter to be passed while creating a dag

Because it's not. You may define the start_date on the tasks.

When Airflow parse the DAG it tried to register tasks into their associated DAG objects. Part of that process it to verify that start_date was provided. The task start_date override the DAG start_date but you must define at least in one of the objects. You can view this in the source code.