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Pyhton3.10 datetime strftime and isocalendar disagreement

I believe that strftime is wrong in the example below. The year should be 2021. isocalendar is right.
Python 3.10.0 (v3.10.0:b494f5935c, Oct 4 2021, 14:59:20) [Clang 12.0.5 (clang-1205.0.22.11)] on darwin
>>> import datetime
>>> datetime.date( 2022, 1, 1 ).strftime( '%Y-%V' )
'2022-52'
>>> datetime.date( 2022, 1, 1 ).isocalendar()
datetime.IsoCalendarDate(year=2021, week=52, weekday=6)

Actually this is the expected behaviour since you are using the %Y format specifier which will return the actual year of the date object.
However you want to use the %G format specifier to return the corresponding ISO year of the date, so try:
import datetime
datetime.date(2022, 1, 1).strftime('%G-%V')
# '2021-52'
Find out more from the docs: https://docs.python.org/3/library/datetime.html#strftime-and-strptime-format-codes

Python3.4 datetime.today() and datetime.now()

Python 3.4.3 (v3.4.3:9b73f1c3e601, Feb 24 2015, 22:43:06) [MSC v.1600 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import datetime
>>> datetime.datetime.today()
datetime.datetime(2015, 8, 30, 23, 17, 6, 937659)
>>> datetime.datetime.now()
datetime.datetime(2015, 8, 30, 23, 17, 14, 378097)
>>>
In Python3.4 datetime.today() and datetime.now() What's the difference?

According to the document of datetime.now(tz=None):
Return the current local date and time. If optional argument tz is None or not specified, this is like today(), but, if possible, supplies more precision than can be gotten from going through a time.time() timestamp (for example, this may be possible on platforms supplying the C gettimeofday() function).
Else tz must be an instance of a class tzinfo subclass, and the current date and time are converted to tz‘s time zone. In this case the result is equivalent to tz.fromutc(datetime.utcnow().replace(tzinfo=tz)).
Thus datetime.now() supplies more precision if possible.

Python - get UTC offset by seconds

Based on this code, how do I get the UTC offset of a given date by seconds. Get UTC offset from time zone name in python
Currently, I have this code:
Python 2.7.3 (default, Jul 3 2012, 19:58:39)
[GCC 4.7.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import pytz
>>> import datetime
>>> offset = datetime.datetime.now(pytz.timezone('US/Pacific')).strftime('%z')
>>> offset
'-0700'
>>> int(offset)*3600
-2520000
>>> int(offset)*360
-252000
>>>
For example, US/Pacific sometimes is -800 hours (probably military time :D) but I need it to be in seconds, ex: -25200.
Shall I just multiply it by 360? Doesn't sound right but who knows.
TIA

>>> import datetime, pytz
>>> melbourne = pytz.timezone("Australia/Melbourne")
>>> melbourne.utcoffset(datetime.datetime.now())
datetime.timedelta(0, 36000)
>>> pacific = pytz.timezone("US/Pacific")
>>> pacific.utcoffset(datetime.datetime.now())
datetime.timedelta(-1, 61200)
>>> -1*86400+61200
-25200
>>> pacific.utcoffset(datetime.datetime.now()).total_seconds()
-25200.0

Convert timestamp since epoch to datetime.datetime

I have the following timestamps since epoch:
Timestamp
1346114717972
1354087827000
How can I convert these timestamps to some specific output format, e.g., mm/dd/yyyy hr:min:sec?
I have tried to convert them to datetime.datetime but it failed:
>>> datetime.datetime.fromtimestamp(1346114717972)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: timestamp out of range for platform time_t
How can I do this?

I would use the time module
>>> import time
>>> time.gmtime(1346114717972/1000.)
time.struct_time(tm_year=2012, tm_mon=8, tm_mday=28, tm_hour=0, tm_min=45, tm_sec=17, tm_wday=1, tm_yday=241, tm_isdst=0)
This shows the timestamp in UTC/GMT time.
The timestamp is divided by 1000 as the stamps you have provided are in milliseconds since the epoch, not seconds.
Then use strftime to format like so:
>>> time.strftime('%m/%d/%Y %H:%M:%S', time.gmtime(1346114717972/1000.))
'08/28/2012 00:45:17'

Assuming millisecond resolution:
import datetime
s = '1346114717972'
fmt = "%Y-%m-%d %H:%M:%S"
# local time
t = datetime.datetime.fromtimestamp(float(s)/1000.)
print t.strftime(fmt) # prints 2012-08-28 02:45:17
# utc time
t_utc = datetime.datetime.utcfromtimestamp(float(s)/1000.)
print t_utc.strftime(fmt) # prints 2012-08-28 00:45:17
Have a look at the documentation for the strftime() and strptime() behavior.

This is the simplest method I've ever seen-
$ python
Python 2.7.5 (default, Nov 6 2016, 00:28:07)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-11)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import time
>>> print(time.strftime('%Y-%m-%dT%H:%M:%S %Z',time.localtime(time.time())))
2018-05-02T13:21:44 IST

Convert ctime to unicode and unicode to ctime python

I have converted a ctime value to unicode
1295478503.6789999
to
'Wed Jan 19 18:08:23 2011'
Can I go backwards?
From the second line to the first?

You want the Python time module, specifically the strptime() function. (How'd you convert from ctime to unicode/string? Probably with time.strftime(). So it makes sense to look for the inverse direction of that, which is time.strptime().)
Here's a good Google query for this, too: http://www.google.com/search?q=python+parse+time+string
Sample:
entropy:~>python
Python 2.6.1 (r261:67515, Jun 24 2010, 21:47:49)
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import time
>>> u = u'Wed Jan 19 18:08:23 2011'
>>> t = time.strptime(u)
>>> t
time.struct_time(tm_year=2011, tm_mon=1, tm_mday=19, tm_hour=18, tm_min=8, tm_sec=23, tm_wday=2, tm_yday=19, tm_isdst=-1)
>>> time.mktime(t)
1295489303.0

import time
time.mktime(time.strptime('Wed Jan 19 18:08:23 2011'))