def _time_grouped(df, index_grouped, col, date_fmt='%Y-%m-%d', hour_fmt='%H:%M'
    ):
    """Return index_grouped as (list of date, list of hour)"""
    date = []
    hour = []
    for item in index_grouped:
        date_val = df.iloc[[item[0]], col].index.strftime(date_fmt).to_list()
        hour_val = df.iloc[[item[0]], col].index.strftime(hour_fmt).to_list()
        date.append(date_val)
        hour.append(hour_val)
    return date, hour
