### Body

Currently `start_date` is mandatory parameter.
For DAGs with `schedule=None` we can relax this requirement as no scheduling calculation needed so the `start_date` parameter isn't used.

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.
(DEFAULT_DATE, None),
            [
                (DEFAULT_DATE + timedelta(days=1), DEFAULT_DATE + timedelta(days=2)),
                (DEFAULT_DATE + timedelta(days=3), DEFAULT_DATE + timedelta(days=4)),
            ],
            TimeRestriction(DEFAULT_DATE, DEFAULT_DATE + timedelta(days=4), True),
        ],
        [
            (DEFAULT_DATE, None),
            [(DEFAULT_DATE, DEFAULT_DATE + timedelta(days=1)), (DEFAULT_DATE, None)],
            TimeRestriction(DEFAULT_DATE, None, True),
        ],
    ],
)
def test__time_restriction(dag_maker, dag_date, tasks_date, restrict):
    with dag_maker("test__time_restriction", start_date=dag_date[0], end_date=dag_date[1]) as dag:
        EmptyOperator(task_id="do1", start_date=tasks_date[0][0], end_date=tasks_date[0][1])
        EmptyOperator(task_id="do2", start_date=tasks_date[1][0], end_date=tasks_date[1][1])
    assert dag._time_restriction == restrict
@pytest.mark.parametrize(
    "tags, should_pass",
    [
        pytest.param([], True, id="empty tags"),
        pytest.param(["a normal tag"], True, id="one tag"),
        pytest.param(["a normal tag", "another normal tag"], True, id="two tags"),
        pytest.param(["a" * 100], True, id="a tag that's of just length 100"),
        pytest.param(["a normal tag", "a" * 101], False, id="two tags and one of them is of length > 100"),
    ],
)
def test__tags_length(tags: list[str], should_pass: bool):