py

import os

class Month:
    name = ""
    dict_days = {}
    def __init__(self, name):
        self.name = name
class Day:
    name = ""
    files = []
    def __init__(self, name):
        self.name = name
    def get_files_count(self):
        print(len(self.files))


files_list = os.listdir("test")
number_files = len(files_list)

dict_month = {}

# переменная count создана для проверки количества создания записей
count = 0

for file in files_list:
    month = file[5] + file[6]
    day = file[8] + file[9]

    # проверяем, существует ли месяц и день в наших словарях
    while True:
        if(month in dict_month):

            if(day in dict_month[month].dict_days):

                break
            else:
                dict_month[month].dict_days[day] = Day(day)

                break
        else:

            dict_month[month] = Month(month)
    count += 1

    dict_month[month].dict_days[day].files.append(file)

# Вывод результата
for m in dict_month:
    print(f"Month is: {m}")
    for d in dict_month[m].dict_days:
        print(f"\tDay is: {d}")
        for f in dict_month[m].dict_days[d].files:
            print(f"\t{f}")