handle_excel_dates.py

import datetime

DATE_SYSTEM_1900_EPOCH = datetime.datetime(1899, 12, 31)
DATE_SYSTEM_1904_EPOCH = DATE_SYSTEM_1900_EPOCH + datetime.timedelta(days=1462)


def _handle_excel_date_system(
    ordinal: Union[str, float],
    _epoch: datetime.datetime
) -> Optional[datetime.datetime]:
    """
    https://stackoverflow.com/a/29387450/5833429
    """
    try:
        ordinal = float(ordinal)
    except ValueError:
        return None
    else:
        # Excel leap year bug, 1900 is not a leap year!
        if ordinal >= 60:
            ordinal -= 1

    return (_epoch + datetime.timedelta(days=ordinal)).replace(microsecond=0)


def date_system_1900_to_datetime(ordinal, _epoch=DATE_SYSTEM_1900_EPOCH) -> datetime.datetime:
    return _handle_excel_date_system(ordinal, _epoch=_epoch)

def date_system_1904_to_datetime(ordinal, _epoch=DATE_SYSTEM_1904_EPOCH) -> datetime.datetime:
    return _handle_excel_date_system(ordinal, _epoch=_epoch)