Check how much ESP8266 RTC drifts with micropython

main.py

import machine
import ntptime
import time
from umqtt.simple import MQTTClient
import sys
import network

def gettimestr():
    rtc=machine.RTC()
    curtime=rtc.datetime()
    _time="%04d" % curtime[0]+"%02d" % curtime[1]+"%02d" % curtime[2]+" "+"%02d" % curtime[4]+"%02d" % curtime[5]
    return _time

wifi = network.WLAN(network.STA_IF)
while not wifi.isconnected():
    print(".")
    time.sleep(1)

#check if gpio4 is pulled down
stoppin = machine.Pin(4,mode=machine.Pin.IN,pull=machine.Pin.PULL_UP)
if stoppin.value()==0:
    print("pin down")
else:
    print("pin up, send message")
    c = MQTTClient("rtc_test", "192.168.0.106")
    c.connect()
    c.publish("/test/rtc",gettimestr())
    c.disconnect()

    # configure RTC.ALARM0 to be able to wake the device
    rtc = machine.RTC()
    rtc.irq(trigger=rtc.ALARM0, wake=machine.DEEPSLEEP)

    # set RTC.ALARM0 to fire after 60 seconds (waking the device)
    rtc.alarm(rtc.ALARM0, 60000)

    # put the device to sleep
    machine.deepsleep()