Micropython module for converting UTC to local time using daylight saving policies.

daylightsaving.py

import utime

# hemisphere [0 = Northern, 1 = Southern]
# week [0 = last week of month, 1..4 = first..fourth]
# month [1 = January; 12 = December]
# weekday [0 = Monday; 6 = Sunday] (day of week) 
# hour (hour at which dst/std changes)
# timezone [-780..780] (offset from UTC in MINUTES - 780min / 60min=13hrs)
class Policy:
    def __init__(self, hemisphere, week, month, weekday, hour, timezone):
        if hemisphere not in [0,1]: raise ValueError('hemisphere must be 0..1')
        if week not in range (0,5): raise ValueError('week must be 0 or 1..4')
        if month not in range (1,13): raise ValueError('month must be 1..12')
        if weekday not in range(0,7): raise ValueError('weekday must be 0..6')
        if hour not in range(0,24): raise ValueError('hour must be 0..23')
        if timezone not in range(-780,781): raise ValueError('timezone must be -780..780')
        self.hemisphere = hemisphere
        self.week = week
        self.month = month
        self.weekday = weekday
        self.hour = hour
        self.timezone = timezone
    def __str__(self):
        self.days = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sum']
        self.abbr = ['last', 'first', 'second', 'third', 'fourth']
        self.months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
        return ('Daylight Saving Policy: daylight saving {} on the {} {} of {} at {:02}:00 hrs (UTC{})').format(
            self.prefix,
            self.abbr[self.week],
            self.days[self.weekday],
            self.months[self.month-1],
            self.hour,
            '' if not self.timezone else '{:+1}'.format(self.timezone/60)
            )
        
class StandardTimePolicy(Policy):
    def __init__(self, hemisphere, week, month, weekday, hour, timezone):
        self.prefix = 'ends'
        super(StandardTimePolicy, self).__init__(hemisphere, week, month, weekday, hour, timezone)

class DaylightSavingPolicy(Policy):
    def __init__(self, hemisphere, week, month, weekday, hour, timezone):
        self.prefix = 'starts'
        super(DaylightSavingPolicy, self).__init__(hemisphere, week, month, weekday, hour, timezone)

class DaylightSaving:
    def __init__(self, dstp, stdp):
        self.dstp = dstp
        self.stdp = stdp
        print(self.dstp)
        print(self.stdp)

    def isleapyear(self, year):
        return ( year % 4 == 0 and year % 100 != 0) or year % 400 ==  0
    
    def dayofmonth(self, week, month, weekday, day, year):
        # Get the first or last day of the month
        t = utime.mktime((year, month, day, 0, 0, 0, 0, 0))
        # Get the weekday of the first or last day of the month
        d = utime.localtime(t)[6]
        increment = lambda d: d + 1 if d < 6 else 0
        decrement = lambda d: d - 1 if d > 0 else 6
        while d != weekday:
            # Increment if start of month else decrement
            day = day + 1 if week else day - 1
            d = increment(d) if week else decrement(d)
        # Increment day of month by number of weeks
        return day + (week - 1) * 7 if week else day
    
    def nthweekday(self, week, month, weekday, hour, year):
        monthlength = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
        if self.isleapyear(year):
            monthlength[1] = 29
        day = 1 if week else monthlength[month-1]
        day = self.dayofmonth(week, month, weekday, day, year)
        return utime.mktime((year, month, day, hour, 0, 0, 0, 0))
    
    def gettfromp(self, p, year):
        return self.nthweekday(p.week, p.month, p.weekday, p.hour, year)
    
    def localtime(self, utc):
        print(f'UTC: {self.ftime(utc)}')
        year = utime.gmtime(utc)[0]
        dst = self.gettfromp(self.dstp, year)
        print(f'Daylight Saving Starts: {self.ftime(dst)}')
        std = self.gettfromp(self.stdp, year)
        print(f'Daylight Saving Ends: {self.ftime(std)}')
        saving = False
        if self.stdp.hemisphere:
            # Sourthern hemisphere
            saving = utc > dst or utc < std
        else:
            # Northern hemisphere
            saving = utc > dst and utc < std
        offset = self.dstp.timezone if saving else self.stdp.timezone
        local = utc + (offset * 60)
        print(f'Local: {self.ftime(local)}')
        return utc + (offset * 60)
    
    def ftime(self, t):
        year, month, day, hour, minute, second, ms, dayinyear = utime.localtime(t)
        return "{:4}-{:02}-{:02}T{:02}:{:02}:{:02}".format(year, month, day, hour, minute, second)

Thanks for this great gist! The text of error should be corrected in line: https://gist.github.com/Beormund/f0f39c72e066da497f6308d1964c9627#file-daylightsaving-py-L16

Done - thanks for spotting.

Hi @Beormund
I found your post about the UDP issue on the micropython forum and it looks like you were also trying to get the fauxmo / echo integration to work on the Pico W, this is exactly what I am trying to accomplish in a hobby project now, did you get it to work on the Pico W ? if yes, do you mind in sharing how you did it? I am stuck at this right now :(
Would you mind sharing your code?? Thank you!