BUG: Adding offset produces NonExistentTimeError

[rhshadrach]

In #36160, Travis had the following failure:

pandas/tests/tseries/offsets/test_offsets_properties.py:88: 
[snip]
---------------------------------- Hypothesis ----------------------------------
Falsifying example: test_on_offset_implementations(
    dt=datetime.datetime(1900, 1, 1, 0, 0, tzinfo=tzfile('/usr/share/zoneinfo/Iceland')),
    offset=<96 * MonthBegins>,
)
You can reproduce this example by temporarily adding @reproduce_failure('5.29.0', b'AAEAMgAAAAAAAAAAAABgAA==') as a decorator on your test case

Can reproduce with:

from datetime import datetime
import pytz
from pandas.tseries.offsets import MonthBegin

dt = datetime(1900, 1, 1, 0, 0, tzinfo=pytz.timezone('Iceland'))
offset = MonthBegin(96)
dt + offset

which produces the trace:

  File "pandas/_libs/tslibs/offsets.pyx", line 422, in pandas._libs.tslibs.offsets.BaseOffset.__add__
  File "pandas/_libs/tslibs/offsets.pyx", line 424, in pandas._libs.tslibs.offsets.BaseOffset.__add__
  File "pandas/_libs/tslibs/offsets.pyx", line 172, in pandas._libs.tslibs.offsets.apply_wraps.wrapper
  File "pandas/_libs/tslibs/timestamps.pyx", line 1317, in pandas._libs.tslibs.timestamps.Timestamp.tz_localize
  File "pandas/_libs/tslibs/tzconversion.pyx", line 63, in pandas._libs.tslibs.tzconversion.tz_localize_to_utc_single
  File "pandas/_libs/tslibs/tzconversion.pyx", line 319, in pandas._libs.tslibs.tzconversion.tz_localize_to_utc
pytz.exceptions.NonExistentTimeError: 1908-01-01 00:00:00

Not sure if this is a bug or an invalid input.

[satyabansahoo2000]

@rhshadrach It's seems to be an bad input. I tried the code offset = MonthBegin(n=90) which works. So, except n=96, it works with all other values.

[mroeschke]

I think the root issue stems from #28610.

datetime object + Offset object does not have any handling whether the resulting timestamp if ambiguous or nonexsitent

[rhshadrach]

Agreed @mroeschke and @hemraj4545, but the question for me is: why is this particular time nonexistent? It happens for me if the minutes are anywhere in 1 to 27, and only in the Iceland timezone. I was also under the expectation that

datetime(1908, 1, 1, 0, 0, tzinfo=pytz.timezone('Iceland'))

would raise as well, but that works fine for me.

[rhshadrach]

Okay - I found it here:

The time zone of Iceland is UT0 (i.e. the same as Greenwich, UK), but Iceland did not adopt the global time zone until January 1908, when GMT‐1 was adopted.

That makes this a duplicate of #28610.

[germainvelard]

Hi,
To me this issue is not closed.
I have the issue with the operation datetime object + Offset object which leads to "pytz.exceptions.NonExistentTimeError: 2019-03-31 02:00:00"
This is due to the fact that this hour is not existent in western Europe due to DST

[rhshadrach]

@germainvelard This issue is closed not because it has been resolved, but rather because it has been found to be a duplicate of another issue as noted above. It seems to me that issue covers what you mention as well, but please let me know if you disagree here.

[germainvelard]

Hi @rhshadrach, thanks for your reply.
It seemed to me that the linked issue was also closed but I was mistaken !
Apologies.