'Efficient parsing for a 1d Pandas/numpy object containing string
representations of dates.
Note: pd.to_datetime is significantly faster when no format string is
passed, and in pandas 0.12.0 the %p strptime directive is not correctly
handled if a format string is explicitly passed, but AM/PM is handled
properly if format=None.
Moreover, we were previously ignoring this parameter unintentionally
because we were incorrectly passing it as a positional.  For all these
reasons, we ignore the format_str parameter when parsing datetimes.'

@staticmethod
def parse_date_str_series(format_str, tz, date_str_series, data_frequency, trading_day):

    if (format_str is not None):
        logger.warn("The    'format_str'    parameter    to    fetch_csv    is    deprecated.    Ignoring    and    defaulting    to    pandas    default    date    parsing.")
        format_str = None
    tz_str = str(tz)
    if (tz_str == pytz.utc.zone):
        parsed = pd.to_datetime(date_str_series.values, format=format_str, utc=True, errors='coerce')
    else:
        parsed = pd.to_datetime(date_str_series.values, format=format_str, errors='coerce').tz_localize(tz_str).tz_convert('UTC')
    if (data_frequency == 'daily'):
        parsed = roll_dts_to_midnight(parsed, trading_day)
    return parsed
