Implementation of NTP and Australian DST in MicroPython

MicroPython_RTC_DST.py

import time, socket
from struct import unpack
from machine import RTC

standardTimeOffset = 60 * 60 * 10 # The base TZ UTC offset in sec, AEST(UTC+10)
summerTimeDifference = 60 * 60 * 1 # The difference between the base TZ and DST TZ in sec, AEDT(UTC+11), 1 hour ahead

rtc = RTC()
lastSync = 0

def isDST(now):
    # Returns true or false adhering to the Australian DST standard(begin DST at 2am (base TZ) on the first Sunday
    # of October, end at 2am(base TZ) on the first Sunday of April.) Provided `now` should always be in base TZ.
    month = now[1]

    if (month >= 11 or month <= 3): return True # Nov, Dec, Jan, Feb, Mar are always summer time
    if (month >= 5 and month <= 9): return False # May, Jun, Jul, Aug, Sep are always standard time

    date = now[2]
    hour = now[3]
    dow = now[6]
    lastSun = date - (dow + 1) # Representing the previous Sunday, even if today is Sunday

    if (month == 10):
        # DST if lastSun was this month or today is changing sunday and after 2am
        return ((lastSun > 0) or (dow == 6 and hour >= 2))

    if (month == 4):
        # DST if lastSun was last month and today isn't changing sunday after 2am
        return ((lastSun <= 0) and (dow != 6 or hour < 2))

def ntpSync():
    # Sets the RTC to the current time in the base TZ, and sets lastSync to the current ticks.
    global lastSync
    NTP_QUERY = bytearray(48)
    NTP_QUERY[0] = 0x1b
    addr = socket.getaddrinfo("au.pool.ntp.org", 123)[0][-1]
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    try:
        s.settimeout(1)
        res = s.sendto(NTP_QUERY, addr)
        msg = s.recv(48)
        tm = time.localtime(unpack("!I", msg[40:44])[0] - 3155673600 + standardTimeOffset)
        rtc.datetime((tm[0], tm[1], tm[2], tm[6] + 1, tm[3], tm[4], tm[5], 0))
        lastSync = time.ticks_ms()
        print("Time synced with NTP")
    except OSError as e:
        if e.args[0] == 110:
            print('NTP timeout!')
        else:
            raise e
    finally:
        s.close()

def getTime():
    # The function that should be used to get the time in other code.
    # Updates the time from NTP if necessary, then returns a tuple of the standard time.localtime() tuple,
    # and the current DST state bool.
    if time.ticks_diff(time.ticks_ms(), lastSync) > 1800000:
        ntpSync()
    now = time.localtime()
    dst = isDST(now)
    if dst:
        now = time.localtime(time.mktime(now) + summerTimeDifference)
    return now, dst

ntpSync() # Initial sync of the RTC