Treatment of Pre-Epoch datetimes in windows

[Jacob-Bishop]

Code Sample

import datetime
datetime.datetime(1953,1,23,0).astimezone(datetime.timezone(datetime.timedelta(days=-1, seconds=57600), 'Pacific Standard Time'))

Problem description

pandas._libs.tslibs.tzconversion._tz_convert_tzlocal_utc calls dt.astimezone(), which fails on Windows for pre-Epoch datetimes (see, e.g., code sample above) with OSError: [Errno 22] Invalid argument. This appears to be related to this issue dateutil/dateutil#197, where time.localtime() can't take negative values on Windows.

Output of pd.show_versions()

INSTALLED VERSIONS ------------------ commit : None python : 3.7.6.final.0 python-bits : 64 OS : Windows OS-release : 10 machine : AMD64 processor : Intel64 Family 6 Model 78 Stepping 3, GenuineIntel byteorder : little LC_ALL : None LANG : None LOCALE : None.None

pandas : 0.25.3
numpy : 1.17.3
pytz : 2019.3
dateutil : 2.8.1
pip : 20.0.2
setuptools : 45.2.0.post20200210
Cython : None
pytest : None
hypothesis : None
sphinx : 2.4.0
blosc : None
feather : None
xlsxwriter : None
lxml.etree : 4.4.1
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 2.10.3
IPython : 7.9.0
pandas_datareader: None
bs4 : 4.8.1
bottleneck : None
fastparquet : None
gcsfs : None
lxml.etree : 4.4.1
matplotlib : 3.1.1
numexpr : None
odfpy : None
openpyxl : 3.0.0
pandas_gbq : None
pyarrow : None
pytables : None
s3fs : None
scipy : 1.3.2
sqlalchemy : None
tables : None
xarray : None
xlrd : 1.2.0
xlwt : None
xlsxwriter : None

Edit

The error appears to be in the datetutil module, not directly in datetime. See the stacktrace below:

Exception ignored in: 'pandas._libs.tslibs.tzconversion._tz_convert_tzlocal_utc' Traceback (most recent call last): File "C:\Users\jbishop\AppData\Roaming\Python\Python37\site-packages\dateutil\tz\_common.py", line 144, in fromutc return f(self, dt) File "C:\Users\jbishop\AppData\Roaming\Python\Python37\site-packages\dateutil\tz\_common.py", line 258, in fromutc dt_wall = self._fromutc(dt) File "C:\Users\jbishop\AppData\Roaming\Python\Python37\site-packages\dateutil\tz\_common.py", line 222, in _fromutc dtoff = dt.utcoffset() File "C:\Users\jbishop\AppData\Roaming\Python\Python37\site-packages\dateutil\tz\tz.py", line 222, in utcoffset if self._isdst(dt): File "C:\Users\jbishop\AppData\Roaming\Python\Python37\site-packages\dateutil\tz\tz.py", line 291, in _isdst dstval = self._naive_is_dst(dt) File "C:\Users\jbishop\AppData\Roaming\Python\Python37\site-packages\dateutil\tz\tz.py", line 260, in _naive_is_dst return time.localtime(timestamp + time.timezone).tm_isdst OSError: [Errno 22] Invalid argument

[mroeschke]

Thanks for the report.

As you mentioned, seems like a deeper bug with dateutil and Windows. We would prefer a fix upstream instead of patching it in pandas.