Improve `--start-date` / `--end-date` documentation to reflect actual accepted formats

[roykoand]

What do you see as an issue?

The CLI help text for date arguments (e.g., --start-date/--end-date) only documents the YYYY-MM-DD format:

airflow/airflow-core/src/airflow/cli/cli_config.py

Lines 170 to 171 in ac085a4

	ARG_START_DATE = Arg(("-s", "--start-date"), help="Override start_date YYYY-MM-DD", type=parsedate)
	ARG_END_DATE = Arg(("-e", "--end-date"), help="Override end_date YYYY-MM-DD", type=parsedate)

However, the actual implementation uses pendelum.parse which accepts a much wider variety of formats beyond what's documented:

airflow/shared/timezones/src/airflow_shared/timezones/timezone.py

Line 191 in ac085a4

return pendulum.parse(string, tz=timezone or _Timezone.initialized_timezone, strict=strict) # type: ignore

With strict=False it accepts a ton of different formats such as:

RFC 3339
2025-12-24T08:30:00Z
2025-12-24T08:30:00-05:00

ISO 8601
2025-12-24
20251224
2025-W52
08:30:00

Solving the problem

I suggest the following help text for discussion:

-s, --start-date
    Override start_date. Common formats:
      YYYY-MM-DD
      YYYY-MM-DDTHH:MM:SS
      YYYY-MM-DDTHH:MM:SS±HH:MM

    Supports any format accepted by pendulum.parse()

Additionally, I think accepting all formats supported by pendulum.parse() may not be ideal, as it could lead to ambiguity and confusion. We could consider limiting the accepted formats to a defined subset to ensure consistency and clarity.

Anything else

No response

Are you willing to submit PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct

[boring-cyborg]

Thanks for opening your first issue here! Be sure to follow the issue template! If you are willing to raise PR to address this issue please do so, no need to wait for approval.

[lx1229]

Any improvement than now? I think this improvement make no value

[Arunodoy18]

hey, I must take on this issue , I think value could be added .
thank you

[roykoand]

Any improvement than now? I think this improvement make no value

@lx1229 I believe the current help text might be a bit confusing for people who have DAGs with, for example, an hourly schedule. If they need to specify --start-date / --end-date with hourly precision, they might be unsure whether that’s supported based on the help text. At the very least, I would explicitly mention that YYYY-MM-DD HH:MM:SS or ISO 8601-compliant (YYYY-MM-DDTHH:MM:SS) is accepted.

[roykoand]

Seems like @Arunodoy18 gave it a shot - #59797