BUG: AmbiguousTimeError when resampling "Atlantic/Azores" to weekly resolution

[kdebrab]

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Reproducible Example

import pandas as pd
ts = pd.Series(1, pd.date_range("2022-10-28", "2022-11-10", tz="Atlantic/Azores", freq="15min"))
ts.resample("W").sum()

Issue Description

Above code raises:

pytz.exceptions.AmbiguousTimeError: Cannot infer dst time from 2022-10-30 00:00:00, try using the 'ambiguous' argument

At first, I thought, maybe that's indeed not possible.

Expected Behavior

But then I saw that no error is raised when resampling to daily resolution:

import pandas as pd
ts = pd.Series(1, pd.date_range("2022-10-28", "2022-11-10", tz="Atlantic/Azores", freq="15min"))
ts.resample("D").sum()

So, if resampling to daily works, shouldn't it also work when resampling to weekly?

Installed Versions

INSTALLED VERSIONS

commit : 2e218d1
python : 3.10.4.final.0
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.19044
machine : AMD64
processor : Intel64 Family 6 Model 140 Stepping 1, GenuineIntel
byteorder : little
LC_ALL : None
LANG : None
LOCALE : English_Belgium.1252
pandas : 1.5.3
numpy : 1.24.2
pytz : 2022.7.1
dateutil : 2.8.2
setuptools : 67.1.0
pip : 23.0
Cython : None
pytest : 6.2.4
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : 3.0.7
lxml.etree : 4.9.2
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.2
IPython : 8.4.0
pandas_datareader: None
bs4 : 4.11.1
bottleneck : 1.3.6
brotli : None
fastparquet : 2023.1.0
fsspec : 2021.11.0
gcsfs : None
matplotlib : 3.6.2
numba : None
numexpr : 2.8.4
odfpy : None
openpyxl : 3.0.10
pandas_gbq : None
pyarrow : 11.0.0
pyreadstat : None
pyxlsb : None
s3fs : 2021.11.0
scipy : 1.10.0
snappy : None
sqlalchemy : None
tables : None
tabulate : 0.8.10
xarray : 2022.12.0
xlrd : None
xlwt : None
zstandard : None
tzdata : None

[topper-123]

This is very weird. I've found that this can be boiled down to:

>>> import pandas as pd
>>> stamp = pd.Timestamp('2022-10-28 00:00:00+0000', tz='Atlantic/Azores')
>>> freq = pd.tseries.offsets.Week(weekday=6)
>>> stamp + freq
AmbiguousTimeError: Cannot infer dst time from 2022-10-30 00:00:00, try using the 'ambiguous' argument

The issue above is that the DST switch happens between 2022-10-30 00:00:00 to 2022-10-30 00:01:00 and it complains about it being badly defined.

I'm not knowledgeable enough about DST to know the correct behavior, i.e. if we should use ambiguous or the above addition should pass and give the same time 7 days forward.

So, I'll leave this open as a bug. We could use some input and/or a PR to fix this.