BUG: Timestamp.unit should reflect changes in components after Timestamp.replace

[wjsi]

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Reproducible Example

import datetime
import pandas as pd

ts = pd.Timestamp("2023-07-15 23:08:12.134567123")
print(ts)  # shows Timestamp('2023-07-16 23:08:12.134567123')
ts2 = pd.Timestamp(datetime.datetime.utcfromtimestamp(int(ts.timestamp())))
ts2 = ts2.replace(microsecond=ts.microsecond, nanosecond=ts.nanosecond)
print(ts2)  # shows Timestamp('2023-07-16 23:08:12.134567123')
assert ts == ts2  # fails

Issue Description

While repr(ts) and repr(ts2) are equal, direct comparison fails.

Expected Behavior

ts and ts2 shall be equal.

Installed Versions

INSTALLED VERSIONS

commit : bdc79c1
python : 3.9.16.final.0
python-bits : 64
OS : Darwin
OS-release : 22.5.0
Version : Darwin Kernel Version 22.5.0: Thu Jun 8 22:22:22 PDT 2023; root:xnu-8796.121.3~7/RELEASE_X86_64
machine : x86_64
processor : i386
byteorder : little
LC_ALL : None
LANG : zh_CN.UTF-8
LOCALE : zh_CN.UTF-8

pandas : 2.2.1
numpy : 1.25.2
pytz : 2023.3.post1
dateutil : 2.8.2
setuptools : 61.2.0
pip : 22.3.1
Cython : 3.0.2
pytest : 8.0.2
hypothesis : 6.46.5
sphinx : 7.2.6
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : None
IPython : 8.1.1
pandas_datareader : None
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : None
bottleneck : 1.3.8
dataframe-api-compat : None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : 3.7.2
numba : None
numexpr : 2.8.4
odfpy : None
openpyxl : 3.1.2
pandas_gbq : None
pyarrow : 11.0.0
pyreadstat : None
python-calamine : None
pyxlsb : None
s3fs : None
scipy : 1.11.1
sqlalchemy : 2.0.19
tables : None
tabulate : None
xarray : None
xlrd : None
zstandard : 0.21.0
tzdata : 2023.3
qtpy : None
pyqt5 : None

[mroeschke]

Thanks for the report. This is due to the unit attributes not matching

In [4]: ts.unit
Out[4]: 'ns'

In [5]: ts2.unit
Out[5]: 'us'

However, I suppose the unit should probably reflect changes when .replace is used.

[diogomsmiranda]

take