BUG: Taking a diff on datetimes yield an OverflowError (or TypeError) in pandas==2.1.0

[mwouts]

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

The following started failing one week ago, with pandas==2.1.0:

def test_datetime_diff(date_min="1677-09-23", date_max="2262-04-10"):
    return pd.to_datetime([date_min, date_max]).diff()

Issue Description

        if to_raise:
>           raise OverflowError("Overflow in int64 addition")
E           OverflowError: Overflow in int64 addition

Expected Behavior

Taking a difference on datetime objects should not raise any exception and return a timedelta.

I have also tried a less extreme date difference, which yields a different error:

def test_datetime_diff_non_extreme_dates(date_min="1997-09-23", date_max="2001-04-10"):
    return pd.to_datetime([date_min, date_max]).diff()

            # GH#29794 enforcing deprecation introduced in GH#23539
>           raise TypeError(f"dtype {data.dtype} cannot be converted to datetime64[ns]")
E           TypeError: dtype timedelta64[ns] cannot be converted to datetime64[ns]

../../miniconda3/envs/itables/lib/python3.11/site-packages/pandas/core/arrays/datetimes.py:2412: TypeError

Installed Versions

``` >>> pd.show_versions()

/home/marc/miniconda3/envs/itables/lib/python3.11/site-packages/_distutils_hack/init.py:33: UserWarning: Setuptools is replacing distutils.
warnings.warn("Setuptools is replacing distutils.")

INSTALLED VERSIONS

commit : ba1cccd
python : 3.11.4.final.0
python-bits : 64
OS : Linux
OS-release : 6.2.0-31-generic
Version : #31~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Wed Aug 16 13:45:26 UTC 2
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 2.1.0
numpy : 1.25.2
pytz : 2022.7
dateutil : 2.8.2
setuptools : 68.0.0
pip : 23.2.1
Cython : None
pytest : 7.4.0
hypothesis : None
sphinx : 5.0.2
blosc : None
feather : None
xlsxwriter : None
lxml.etree : 4.9.2
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.2
IPython : 8.12.2
pandas_datareader : None
bs4 : 4.12.2
bottleneck : 1.3.5
dataframe-api-compat: None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : None
numba : None
numexpr : 2.8.4
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : 11.0.0
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : 2.0.20
tables : None
tabulate : 0.9.0
xarray : None
xlrd : None
zstandard : None
tzdata : 2023.3
qtpy : 2.2.0
pyqt5 : None

</details>

[paulreece]

I can confirm this is a bug on the main branch. I ran both test cases locally on the main branch 2.1.0 and received errors on each.

[mwouts]

Awesome, thank you for the fix!

[mwouts]

FYI I see a partial return of this issue in pandas==2.2.0. The non-extreme version of the test pass, but this one fails:

def test_datetime_diff(date_min="1677-09-23", date_max="2262-04-10"):
    return pd.to_datetime([date_min, date_max]).diff()

I will be using less extreme dates for my tests, but I still prefer to let you know. The precise error is the following:

date_min = '1677-09-23', date_max = '2262-04-10'

    def test_datetime_diff(date_min="1677-09-23", date_max="2262-04-10"):
>       return pd.to_datetime([date_min, date_max]).diff()

itables/sample_dfs.py:422: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
../../miniconda3/envs/itables/lib/python3.11/site-packages/pandas/core/indexes/base.py:7132: in diff
    return Index(self.to_series().diff(periods))
../../miniconda3/envs/itables/lib/python3.11/site-packages/pandas/core/series.py:3110: in diff
    result = algorithms.diff(self._values, periods)
../../miniconda3/envs/itables/lib/python3.11/site-packages/pandas/core/algorithms.py:1379: in diff
    return op(arr, arr.shift(n))
../../miniconda3/envs/itables/lib/python3.11/site-packages/pandas/core/ops/common.py:76: in new_method
    return method(self, other)
../../miniconda3/envs/itables/lib/python3.11/site-packages/pandas/core/arrays/datetimelike.py:1457: in __sub__
    result = self._sub_datetime_arraylike(other)
../../miniconda3/envs/itables/lib/python3.11/site-packages/pandas/core/arrays/datetimelike.py:1154: in _sub_datetime_arraylike
    return self._sub_datetimelike(other)
../../miniconda3/envs/itables/lib/python3.11/site-packages/pandas/core/arrays/datetimelike.py:1169: in _sub_datetimelike
    res_values = add_overflowsafe(self.asi8, np.asarray(-other_i8, dtype="i8"))
np_datetime.pyx:709: in pandas._libs.tslibs.np_datetime.add_overflowsafe
    ???
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

>   ???
E   OverflowError: Overflow in int64 addition

np_datetime.pyx:743: OverflowError

[m1n0]

Could this fix be ported to v1 version as well? Or is v1 completely dead at this point?