OpenBB-finance/OpenBB · error · ValueError

Start date '{dt_start_date}' is after the last date availabl

Error message

Start date '{dt_start_date}' is after the last date available for Fama-French '{df.index[-1]}'

What it means

Thrown in the Fama-French helper (openbb_quantitative/helpers.py) after loading the factor dataset: the user-supplied start_date (parsed as %Y-%m-%d) is later than the maximum date in the loaded Fama-French index. This guards df.loc[start_date:end_date] from producing an empty slice.

Source

Thrown at openbb_platform/extensions/quantitative/openbb_quantitative/helpers.py:53

                    skiprows=3,
                )

    df = df[df["Date"].apply(lambda x: len(str(x).strip()) == 6)]
    df["Date"] = df["Date"].astype(str) + "01"
    df["Date"] = to_datetime(df["Date"], format="%Y%m%d")
    df["MKT-RF"] = to_numeric(df["MKT-RF"], downcast="float")
    df["SMB"] = to_numeric(df["SMB"], downcast="float")
    df["HML"] = to_numeric(df["HML"], downcast="float")
    df["RF"] = to_numeric(df["RF"], downcast="float")
    df["MKT-RF"] = df["MKT-RF"] / 100
    df["SMB"] = df["SMB"] / 100
    df["HML"] = df["HML"] / 100
    df["RF"] = df["RF"] / 100
    df = df.set_index("Date")

    dt_start_date = to_datetime(start_date, format="%Y-%m-%d")
    if dt_start_date > df.index.max():
        raise ValueError(
            f"Start date '{dt_start_date}' is after the last date available for Fama-French '{df.index[-1]}'"
        )

    df = df.loc[start_date:end_date]  # type: ignore

    return df


def validate_window(input_data: Union["Series", "DataFrame"], window: int) -> None:
    """Validate the window input.

    Parameters
    ----------
    input_data : Union[Series, DataFrame]
        The input data to be validated.
    window : int
        The window to be validated.

View on GitHub (pinned to 3e071fcc2c)

Solutions

  1. Set start_date to a date on or before the dataset's last available date shown in the message.
  2. Update the Fama-French dataset / upgrade openbb-quantitative so the packaged file is current.
  3. Format dates strictly as YYYY-MM-DD strings.
  4. If you need recent factors, fetch the latest files from the Fama-French library and supply them through the supported data path.

Example fix

# before
res = obb.quantitative.fama_french(...)  # start_date='2026-01-01', data ends 2025-12

# after
res = obb.quantitative.fama_french(..., start_date='2025-01-01')
Defensive patterns

Strategy: validation

Validate before calling

from datetime import datetime
start = datetime.strptime(start_date, "%Y-%m-%d")
last = fama_french_df.index.max()
assert start <= last, f"start_date {start.date()} is after last available {last.date()}; use <= {last.date()}"

Type guard

def start_within_data(start_date: str, df) -> bool:
    from datetime import datetime
    return datetime.strptime(start_date, "%Y-%m-%d") <= df.index.max()

Try / catch

try:
    res = obb.quantitative.fama_french(..., start_date=start_date)
except ValueError as e:
    if "after the last date available" in str(e):
        start_date = str(df.index.max().date())  # clamp to dataset end
        res = obb.quantitative.fama_french(..., start_date=start_date)
    else:
        raise

Prevention

When it happens

Trigger: Calling the Fama-French based quantitative endpoints with a start_date after the newest row of the packaged/downloaded factor file (df.index.max()), e.g. requesting data from a date beyond the dataset's last update.

Common situations: Stale local Fama-French dataset behind the installed OpenBB version; requesting current-year dates when the packaged data ends earlier; date strings not matching YYYY-MM-DD causing unexpected parsed values.

Related errors

AI-assisted analysis of OpenBB-finance/OpenBB@3e071fcc2c (2026-08-14). Data as JSON: /api/errors/5cb12b02b111de58. Report an issue: GitHub.