BUG: DatetimeTZDtype.base always returns dtype with ns resolution

[shwina]

Pandas version checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

>>> pd.DatetimeTZDtype("ms", "America/New_York").base
dtype('<M8[ns]')

Issue Description

The .base attribute always returns a numpy dtype with ns resolution.

Expected Behavior

I would expect the resolution to match the resolution of the DatetimeTZDtype.

Installed Versions

INSTALLED VERSIONS

commit : 478d340
python : 3.10.9.final.0
python-bits : 64
OS : Linux
OS-release : 5.15.0-67-generic
Version : #74~20.04.1-Ubuntu SMP Wed Feb 22 14:52:34 UTC 2023
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 2.0.0
numpy : 1.23.5
pytz : 2022.7.1
dateutil : 2.8.2
setuptools : 65.6.3
pip : 22.3.1
Cython : 0.29.33
pytest : 7.2.1
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.2
IPython : None
pandas_datareader: None
bs4 : None
bottleneck : None
brotli : None
fastparquet : None
fsspec : 2023.1.0
gcsfs : None
matplotlib : None
numba : 0.56.4
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : 10.0.0
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : None
snappy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
zstandard : None
tzdata : 2023.3
qtpy : None
pyqt5 : None

[shwina]

#52706 closed this issue