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BUG: Fix inconsistency with DateOffset near DST #61870

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BUG: Fix inconsistency with DateOffset near DST #61870

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37aeccd
Fix inconsistency with DateOffset near DST
arthurlw Jul 16, 2025
cbcd775
Updated with reviewer comments
arthurlw Jul 17, 2025
cd7c0d1
Moved relativedelta imports to the top
arthurlw Jul 17, 2025
da7eb58
Added GH reference
arthurlw Jul 18, 2025
e02dc29
whatsnew
arthurlw Jul 18, 2025
e8f5e7b
Merge branch 'main' into DateOffset_inconsistency_near_DST
arthurlw Jul 18, 2025
91397e3
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Jul 18, 2025
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9 changes: 5 additions & 4 deletions pandas/_libs/tslibs/offsets.pyx
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,8 @@ from cpython.datetime cimport (

import warnings

from dateutil.relativedelta import relativedelta
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is this imported at top-level anywhere else in the repo? not sure but we might be delaying this import to improve import pandas as pd speed

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On main it is a localized import in this file on line 328

    if all(k in kwds_use_relativedelta for k in kwds_no_nanos):
        from dateutil.relativedelta import relativedelta

        return relativedelta(**kwds_no_nanos), True


import_datetime()

import numpy as np
Expand Down Expand Up @@ -283,8 +285,9 @@ _relativedelta_kwds = {"years", "months", "weeks", "days", "year", "month",

cdef _determine_offset(kwds):
if not kwds:
# GH 45643/45890: (historically) defaults to 1 day
return timedelta(days=1), False
# GH 45643, 45890: (historically) defaults to 1 day
# GH 61870: changed from timedelta to relativedelta
return relativedelta(days=1), True

if "millisecond" in kwds:
raise NotImplementedError(
Expand Down Expand Up @@ -325,8 +328,6 @@ cdef _determine_offset(kwds):
kwds_no_nanos["microseconds"] = kwds_no_nanos.get("microseconds", 0) + micro

if all(k in kwds_use_relativedelta for k in kwds_no_nanos):
from dateutil.relativedelta import relativedelta

return relativedelta(**kwds_no_nanos), True

raise ValueError(
Expand Down
13 changes: 11 additions & 2 deletions pandas/tests/tseries/offsets/test_offsets.py
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Expand Up @@ -9,6 +9,7 @@
timedelta,
)

from dateutil.relativedelta import relativedelta
import numpy as np
import pytest

Expand Down Expand Up @@ -1095,9 +1096,9 @@ def test_dateoffset_misc():

@pytest.mark.parametrize("n", [-1, 1, 3])
def test_construct_int_arg_no_kwargs_assumed_days(n):
# GH 45890, 45643
# GH 45643, 45890, 61870
offset = DateOffset(n)
assert offset._offset == timedelta(1)
assert offset._offset == relativedelta(days=1)
result = Timestamp(2022, 1, 2) + offset
expected = Timestamp(2022, 1, 2 + n)
assert result == expected
Expand Down Expand Up @@ -1227,3 +1228,11 @@ def test_is_yqm_start_end():
def test_multiply_dateoffset_typeerror(left, right):
with pytest.raises(TypeError, match="Cannot multiply"):
left * right


def test_dateoffset_days_vs_n_near_dst_transition():
ts = Timestamp("2022-10-30", tz="Europe/Brussels")
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GH ref


offset_days = ts + offsets.DateOffset(days=1)
offset_n = ts + offsets.DateOffset(1)
assert offset_days == offset_n
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