[issue38645] datetime.datetime.fromtimestamp(0, tzlocal()) throws error

[Ammar Askar]

Ammar Askar <ammar at ammaraskar.com> added the comment:

It is windows specific, but I don't think this is a dateutil bug rather than the python stdlib:

Python 3.6.5 (v3.6.5:f59c0932b4, Mar 28 2018, 16:07:46) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import datetime
>>> from dateutil.tz import tzlocal
>>> print(datetime.datetime.fromtimestamp(0, tzlocal()))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "D:\Python365\lib\site-packages\dateutil\tz\_common.py", line 144, in fromutc
    return f(self, dt)
  File "D:\Python365\lib\site-packages\dateutil\tz\_common.py", line 258, in fromutc
    dt_wall = self._fromutc(dt)
  File "D:\Python365\lib\site-packages\dateutil\tz\_common.py", line 238, in _fromutc
    dtdst = enfold(dt, fold=1).dst()
  File "D:\Python365\lib\site-packages\dateutil\tz\tz.py", line 225, in dst
    if self._isdst(dt):
  File "D:\Python365\lib\site-packages\dateutil\tz\tz.py", line 288, in _isdst
    if self.is_ambiguous(dt):
  File "D:\Python365\lib\site-packages\dateutil\tz\tz.py", line 250, in is_ambiguous
    (naive_dst != self._naive_is_dst(dt - self._dst_saved)))
  File "D:\Python365\lib\site-packages\dateutil\tz\tz.py", line 254, in _naive_is_dst
    return time.localtime(timestamp + time.timezone).tm_isdst
OSError: [Errno 22] Invalid argument


As you can see, none of that backtrace is within Python, it's all inside dateutil code. More than likely they are calling `time.localtime` with a value of less than 0 which throws an error on Windows. (see also issue29097)

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nosy: +ammar2

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<https://bugs.python.org/issue38645>
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