I wrote a small module to convert UTC to Local Time using daylight saving policies. It might help.
Code: Select all
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('weekday 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:
# Southern 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)
Code: Select all
import daylightsaving
import utime
# Example for UK Daylight Saving (BST)
# Daylight Saving starts on last Sunday of March at 1AM
# 0 = Northern hemisphere
# 0 = Last week of the month
# 3 = March
# 6 = Sunday
# 1 = 1AM
# Time offset = 60 mins (GMT+1)
dst = DaylightSavingPolicy(0, 0, 3, 6, 1, 60)
# Daylight Saving ends on last Snday of October at 2AM
# 0 = Northern hemisphere
# 0 = Last week of the month
# 10 = October
# 6 = Sunday
# 2 = 2AM
# Time offset = 0 mins (GMT/UTC)
std = StandardTimePolicy(0, 0, 10, 6, 2, 0)
# Create a DaylightSaving object passing in policies
ds = DaylightSaving(dst, std)
# Obtain UTC time in seconds since epoch (from NTP Server or RTC etc)
utc = utime.mktime((2022, 7, 27, 13, 30, 0, 0, 0))
# Calculate local time passing in UTC time
local = ds.localtime(utc)
Please leave comments on the gist if you find any problems or can suggest improvements.
