How to work with RTC correctly?

[kropochev]

There is M5Stack StickC Plus2 with firmware UIFlow2.0 v.2.1.7.

I load the following code:

import os, sys, io
import M5
from M5 import *
from hardware import *
import time

rtc = None

def setup():
  global rtc
  rtc = RTC()
  rtc.init((2024, 11, 4, 0, 21, 51, 15, 504))
  M5.begin()

def loop():
  global rtc
  M5.update()
  print(time.mktime(time.localtime()))
  print(rtc.datetime())

if __name__ == '__main__':
  try:
    setup()
    while True:
      loop()
  except (Exception, KeyboardInterrupt) as e:
    try:
      from utility import print_error_msg
      print_error_msg(e)
    except ImportError:
      print("please update to latest firmware")

I see the current time and date in the console, then I comment the line

# rtc.init((2024, 11, 4, 0, 21, 51, 15, 504))

and boot again and see the current time in the console.

But if I turn off the board with the button on the left side and then turn it on, the time will reset to:
(2000, 2, 2, 3, 10, 13, 29, 894534)
949468409

Why does this happen? Shouldn't the time be saved when turned off?