def get_zeroth_quarter_idx(self, stacked_last_per_qtr):
        previous_releases_per_date = stacked_last_per_qtr.loc[
            stacked_last_per_qtr[EVENT_DATE_FIELD_NAME] <=
            stacked_last_per_qtr.index.get_level_values(SIMULATION_DATES)
        ].groupby(
            level=[SIMULATION_DATES, SID_FIELD_NAME],
            as_index=False,
        ).nth(-1)
        return previous_releases_per_date.index