From 0537d03be6be3502aec8f051a29b88cf1c8fa264 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 06:36:50 -0600
Subject: [PATCH 01/30] TST: add regression tests for GH#63388 (DatetimeIndex
 copy behavior)

---
 .../copy_view/index/test_datetimeindex.py     | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/pandas/tests/copy_view/index/test_datetimeindex.py b/pandas/tests/copy_view/index/test_datetimeindex.py
index 6194ea8b122c9..6b289c856fd93 100644
--- a/pandas/tests/copy_view/index/test_datetimeindex.py
+++ b/pandas/tests/copy_view/index/test_datetimeindex.py
@@ -1,3 +1,4 @@
+import numpy as np
 import pytest
 
 from pandas import (
@@ -7,6 +8,7 @@
     date_range,
 )
 import pandas._testing as tm
+from pandas.tests.copy_view.util import get_array
 
 pytestmark = pytest.mark.filterwarnings(
     "ignore:Setting a value on a view:FutureWarning"
@@ -54,3 +56,31 @@ def test_index_values():
     idx = date_range("2019-12-31", periods=3, freq="D")
     result = idx.values
     assert result.flags.writeable is False
+
+
+def test_constructor_copy_input_datetime_ndarray_default():
+    # GH 63388
+    arr = np.array(["2020-01-01", "2020-01-02"], dtype="datetime64[ns]")
+    idx = DatetimeIndex(arr)
+    assert not np.shares_memory(arr, get_array(idx))
+
+
+def test_constructor_copy_input_datetime_ea_default():
+    # GH 63388
+    arr = np.array(["2020-01-01", "2020-01-02"], dtype="datetime64[ns]")
+    idx = DatetimeIndex(arr)
+    assert not tm.shares_memory(arr, idx.array)
+
+
+def test_series_from_temporary_index_readonly_data():
+    # GH 63388
+    arr = np.array(["2020-01-01", "2020-01-02"], dtype="datetime64[ns]")
+    arr.flags.writeable = False
+    ser = Series(DatetimeIndex(arr))
+    assert not np.shares_memory(arr, get_array(ser))
+    ser.iloc[0] = Timestamp("2020-01-01")
+    expected = Series(
+        [Timestamp("2020-01-01"), Timestamp("2020-01-02")], 
+        dtype="datetime64[ns]"
+    )
+    tm.assert_series_equal(ser, expected)

From 3b7b85b4e3bba9b4e71a4c204c261b9043abf60f Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 07:07:19 -0600
Subject: [PATCH 02/30] ENH: Copy inputs in DatetimeIndex constructor by
 default (GH#63388)

---
 pandas/core/indexes/datetimes.py | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index a07e18b1892fd..21944a0e62c79 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -42,6 +42,7 @@
     ArrowDtype,
     DatetimeTZDtype,
 )
+from pandas.core.dtypes.astype import astype_is_view
 from pandas.core.dtypes.generic import ABCSeries
 from pandas.core.dtypes.missing import is_valid_na_for_dtype
 
@@ -49,6 +50,7 @@
     DatetimeArray,
     tz_to_dtype,
 )
+from pandas.core.arrays import ExtensionArray
 import pandas.core.common as com
 from pandas.core.indexes.base import (
     Index,
@@ -181,8 +183,13 @@ class DatetimeIndex(DatetimeTimedeltaMixin):
         If True parse dates in `data` with the year first order.
     dtype : numpy.dtype or DatetimeTZDtype or str, default None
         Note that the only NumPy dtype allowed is `datetime64[ns]`.
-    copy : bool, default False
-        Make a copy of input ndarray.
+    copy : bool, default None
+        Whether to copy input data, only relevant for array, Series, and Index
+        inputs (for other input, e.g. a list, a new array is created anyway).
+        Defaults to True for array input and False for Index/Series.
+        Set to False to avoid copying array input at your own risk (if you
+        know the input data won't be modified elsewhere).
+        Set to True to force copying Series/Index up front.
     name : label, default None
         Name to be stored in the index.
 
@@ -669,7 +676,7 @@ def __new__(
         dayfirst: bool = False,
         yearfirst: bool = False,
         dtype: Dtype | None = None,
-        copy: bool = False,
+        copy: bool | None = None,
         name: Hashable | None = None,
     ) -> Self:
         if is_scalar(data):
@@ -679,6 +686,13 @@ def __new__(
 
         name = maybe_extract_name(name, data, cls)
 
+        if isinstance(data, (ExtensionArray, np.ndarray)):
+            # GH 63388
+            if copy is not False:
+                if dtype is None or astype_is_view(data.dtype, dtype):
+                    data = data.copy()
+                    copy = False
+
         if (
             isinstance(data, DatetimeArray)
             and freq is lib.no_default

From 67eaf0568b5769d915df9822249c6e2d69eed7ae Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 07:26:49 -0600
Subject: [PATCH 03/30] CLN: change test name to include datetimeindex for
 clarity

---
 pandas/tests/copy_view/index/test_datetimeindex.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/tests/copy_view/index/test_datetimeindex.py b/pandas/tests/copy_view/index/test_datetimeindex.py
index 6b289c856fd93..eb4dd7744bbdc 100644
--- a/pandas/tests/copy_view/index/test_datetimeindex.py
+++ b/pandas/tests/copy_view/index/test_datetimeindex.py
@@ -72,7 +72,7 @@ def test_constructor_copy_input_datetime_ea_default():
     assert not tm.shares_memory(arr, idx.array)
 
 
-def test_series_from_temporary_index_readonly_data():
+def test_series_from_temporary_datetimeindex_readonly_data():
     # GH 63388
     arr = np.array(["2020-01-01", "2020-01-02"], dtype="datetime64[ns]")
     arr.flags.writeable = False

From f59ab9e39ff1b6d05a47a45ba8a606db45368e6c Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 07:33:31 -0600
Subject: [PATCH 04/30] TST: Add regression tests for GH#63388 (TimedeltaIndex
 copy behavior)

---
 .../copy_view/index/test_timedeltaindex.py    | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/pandas/tests/copy_view/index/test_timedeltaindex.py b/pandas/tests/copy_view/index/test_timedeltaindex.py
index 6984df86b00e3..d476acb6248b9 100644
--- a/pandas/tests/copy_view/index/test_timedeltaindex.py
+++ b/pandas/tests/copy_view/index/test_timedeltaindex.py
@@ -1,3 +1,4 @@
+import numpy as np
 import pytest
 
 from pandas import (
@@ -7,6 +8,7 @@
     timedelta_range,
 )
 import pandas._testing as tm
+from pandas.tests.copy_view.util import get_array
 
 pytestmark = pytest.mark.filterwarnings(
     "ignore:Setting a value on a view:FutureWarning"
@@ -27,3 +29,31 @@ def test_timedeltaindex(cons):
     expected = idx.copy(deep=True)
     ser.iloc[0] = Timedelta("5 days")
     tm.assert_index_equal(idx, expected)
+
+
+def test_constructor_copy_input_timedelta_ndarray_default():
+    # GH 63388
+    arr = np.array([1, 2], dtype="timedelta64[ns]")
+    idx = TimedeltaIndex(arr)
+    assert not np.shares_memory(arr, get_array(idx))
+
+
+def test_constructor_copy_input_timedelta_ea_default():
+    # GH 63388
+    arr = np.array([1, 2], dtype="timedelta64[ns]")
+    idx = TimedeltaIndex(arr)
+    assert not tm.shares_memory(arr, idx.array)
+
+
+def test_series_from_temporary_timedeltaindex_readonly_data():
+    # GH 63388
+    arr = np.array([1, 2], dtype="timedelta64[ns]")
+    arr.flags.writeable = False 
+    ser = Series(TimedeltaIndex(arr))
+    assert not np.shares_memory(arr, get_array(ser))
+    ser.iloc[0] = Timedelta(days=1)
+    expected = Series(
+        [Timedelta(days=1), Timedelta(nanoseconds=2)],
+        dtype="timedelta64[ns]"
+    )
+    tm.assert_series_equal(ser, expected)

From 9221e5a0b7c21b29631bb99bfd3e19894208b043 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 07:41:05 -0600
Subject: [PATCH 05/30] ENH: Copy inputs in TimedeltaIndex constructor by
 default (GH#63388)

---
 pandas/core/indexes/timedeltas.py | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/pandas/core/indexes/timedeltas.py b/pandas/core/indexes/timedeltas.py
index 2a3d5137242d0..15cf9b894e19e 100644
--- a/pandas/core/indexes/timedeltas.py
+++ b/pandas/core/indexes/timedeltas.py
@@ -7,6 +7,8 @@
     cast,
 )
 
+import numpy as np
+
 from pandas._libs import (
     index as libindex,
     lib,
@@ -23,9 +25,11 @@
     is_scalar,
     pandas_dtype,
 )
+from pandas.core.dtypes.astype import astype_is_view
 from pandas.core.dtypes.dtypes import ArrowDtype
 from pandas.core.dtypes.generic import ABCSeries
 
+from pandas.core.arrays import ExtensionArray
 from pandas.core.arrays.timedeltas import TimedeltaArray
 import pandas.core.common as com
 from pandas.core.indexes.base import (
@@ -81,8 +85,13 @@ class TimedeltaIndex(DatetimeTimedeltaMixin):
     dtype : numpy.dtype or str, default None
         Valid ``numpy`` dtypes are ``timedelta64[ns]``, ``timedelta64[us]``,
         ``timedelta64[ms]``, and ``timedelta64[s]``.
-    copy : bool
-        Make a copy of input array.
+    copy : bool, default None
+        Whether to copy input data, only relevant for array, Series, and Index
+        inputs (for other input, e.g. a list, a new array is created anyway).
+        Defaults to True for array input and False for Index/Series.
+        Set to False to avoid copying array input at your own risk (if you
+        know the input data won't be modified elsewhere).
+        Set to True to force copying Series/Index input up front.
     name : object
         Name to be stored in the index.
 
@@ -158,11 +167,18 @@ def __new__(
         data=None,
         freq=lib.no_default,
         dtype=None,
-        copy: bool = False,
+        copy: bool | None = None,
         name=None,
     ):
         name = maybe_extract_name(name, data, cls)
 
+        if isinstance(data, (ExtensionArray, np.ndarray)):
+            # GH 63388
+            if copy is not False:
+                if dtype is None or astype_is_view(data.dtype, dtype):
+                    data = data.copy()
+                    copy = False
+
         if is_scalar(data):
             cls._raise_scalar_data_error(data)
 

From 32ee4dcaa5c5a9a4891565c3d470bcbddcabb368 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 07:48:27 -0600
Subject: [PATCH 06/30] TST: correct test to use array instead of np.array

---
 pandas/tests/copy_view/index/test_datetimeindex.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pandas/tests/copy_view/index/test_datetimeindex.py b/pandas/tests/copy_view/index/test_datetimeindex.py
index eb4dd7744bbdc..f223d6236e032 100644
--- a/pandas/tests/copy_view/index/test_datetimeindex.py
+++ b/pandas/tests/copy_view/index/test_datetimeindex.py
@@ -6,6 +6,7 @@
     Series,
     Timestamp,
     date_range,
+    array
 )
 import pandas._testing as tm
 from pandas.tests.copy_view.util import get_array
@@ -67,7 +68,7 @@ def test_constructor_copy_input_datetime_ndarray_default():
 
 def test_constructor_copy_input_datetime_ea_default():
     # GH 63388
-    arr = np.array(["2020-01-01", "2020-01-02"], dtype="datetime64[ns]")
+    arr = array(["2020-01-01", "2020-01-02"], dtype="datetime64[ns]")
     idx = DatetimeIndex(arr)
     assert not tm.shares_memory(arr, idx.array)
 

From b55f4a04700f97a9e2bb5c17705f79e3101aacc5 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 07:50:05 -0600
Subject: [PATCH 07/30] TST: correct test to use array instead of np.array

---
 pandas/tests/copy_view/index/test_timedeltaindex.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pandas/tests/copy_view/index/test_timedeltaindex.py b/pandas/tests/copy_view/index/test_timedeltaindex.py
index d476acb6248b9..0888665e469eb 100644
--- a/pandas/tests/copy_view/index/test_timedeltaindex.py
+++ b/pandas/tests/copy_view/index/test_timedeltaindex.py
@@ -6,6 +6,7 @@
     Timedelta,
     TimedeltaIndex,
     timedelta_range,
+    array
 )
 import pandas._testing as tm
 from pandas.tests.copy_view.util import get_array
@@ -40,7 +41,7 @@ def test_constructor_copy_input_timedelta_ndarray_default():
 
 def test_constructor_copy_input_timedelta_ea_default():
     # GH 63388
-    arr = np.array([1, 2], dtype="timedelta64[ns]")
+    arr = array([1, 2], dtype="timedelta64[ns]")
     idx = TimedeltaIndex(arr)
     assert not tm.shares_memory(arr, idx.array)
 

From 91e78dae32323ee8f4cc82632980f2c2ce9b555a Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 07:56:07 -0600
Subject: [PATCH 08/30] TST: Add regression tests for GH#63388 (PeriodIndex
 copy behavior)

---
 .../tests/copy_view/index/test_periodindex.py | 24 +++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/pandas/tests/copy_view/index/test_periodindex.py b/pandas/tests/copy_view/index/test_periodindex.py
index 2887b191038d2..29fce0fb6290b 100644
--- a/pandas/tests/copy_view/index/test_periodindex.py
+++ b/pandas/tests/copy_view/index/test_periodindex.py
@@ -1,3 +1,4 @@
+import numpy as np
 import pytest
 
 from pandas import (
@@ -5,8 +6,10 @@
     PeriodIndex,
     Series,
     period_range,
+    array
 )
 import pandas._testing as tm
+from pandas.tests.copy_view.util import get_array
 
 pytestmark = pytest.mark.filterwarnings(
     "ignore:Setting a value on a view:FutureWarning"
@@ -21,3 +24,24 @@ def test_periodindex(box):
     expected = idx.copy(deep=True)
     ser.iloc[0] = Period("2020-12-31")
     tm.assert_index_equal(idx, expected)
+
+
+def test_constructor_copy_input_period_ea_default():
+    # GH 63388
+    arr = array(['2020-01-01', '2020-01-02'], dtype='period[D]')
+    idx = PeriodIndex(arr)
+    assert not tm.shares_memory(arr, idx.array)
+
+
+def test_series_from_temporary_periodindex_readonly_data():
+    # GH 63388
+    arr = array(['2020-01-01', '2020-01-02'], dtype='period[D]')
+    arr._ndarray.flags.writeable = False
+    ser = Series(PeriodIndex(arr))
+    assert not np.shares_memory(arr._ndarray, get_array(ser))
+    ser.iloc[0] = Period('2022-01-01', freq='D')
+    expected = Series(
+        [Period('2022-01-01', freq='D'), Period('2020-01-02', freq='D')], 
+        dtype='period[D]'
+    )
+    tm.assert_series_equal(ser, expected)

From 12527829880525cfdbcfb903c1e981460c699660 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 08:00:40 -0600
Subject: [PATCH 09/30] ENH: Copy inputs in PeriodIndex constructor by default
 (GH#63388)

---
 pandas/core/indexes/period.py | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index c3ad466a114a9..22118ae065aed 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -27,11 +27,13 @@
     set_module,
 )
 
+from pandas.core.dtypes.astype import astype_is_view
 from pandas.core.dtypes.common import is_integer
 from pandas.core.dtypes.dtypes import PeriodDtype
 from pandas.core.dtypes.generic import ABCSeries
 from pandas.core.dtypes.missing import is_valid_na_for_dtype
 
+from pandas.core.arrays import ExtensionArray
 from pandas.core.arrays.period import (
     PeriodArray,
     period_array,
@@ -101,8 +103,13 @@ class PeriodIndex(DatetimeIndexOpsMixin):
         One of pandas period strings or corresponding objects.
     dtype : str or PeriodDtype, default None
         A dtype from which to extract a freq.
-    copy : bool
-        Make a copy of input ndarray.
+    copy : bool, default None
+        Whether to copy input data, only relevant for array, Series, and Index
+        inputs (for other input, e.g. a list, a new array is created anyway).
+        Defaults to True for array input and False for Index/Series.
+        Set to False to avoid copying array input at your own risk (if you
+        know the input data won't be modified elsewhere).
+        Set to True to force copying Series/Index input up front.
     name : str, default None
         Name of the resulting PeriodIndex.
 
@@ -220,7 +227,7 @@ def __new__(
         data=None,
         freq=None,
         dtype: Dtype | None = None,
-        copy: bool = False,
+        copy: bool | None = None,
         name: Hashable | None = None,
     ) -> Self:
         refs = None
@@ -231,6 +238,13 @@ def __new__(
 
         freq = validate_dtype_freq(dtype, freq)
 
+        if isinstance(data, (ExtensionArray, np.ndarray)):
+            # GH 63388
+            if copy is not False:
+                if dtype is None or astype_is_view(data.dtype, dtype):
+                    data = data.copy()
+                    copy = False
+
         # PeriodIndex allow PeriodIndex(period_index, freq=different)
         # Let's not encourage that kind of behavior in PeriodArray.
 

From 923c949423ff95fd70c67aee511250f8eabfa92f Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 08:04:34 -0600
Subject: [PATCH 10/30] TST: Add regression tests for GH#63388 (IntervalIndex
 copy behavior)

---
 .../copy_view/index/test_intervalindex.py     | 32 +++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 pandas/tests/copy_view/index/test_intervalindex.py

diff --git a/pandas/tests/copy_view/index/test_intervalindex.py b/pandas/tests/copy_view/index/test_intervalindex.py
new file mode 100644
index 0000000000000..630687dc0c102
--- /dev/null
+++ b/pandas/tests/copy_view/index/test_intervalindex.py
@@ -0,0 +1,32 @@
+import numpy as np
+
+from pandas import (
+    IntervalIndex,
+    Series,
+    Interval,
+    array,
+)
+import pandas._testing as tm
+from pandas.tests.copy_view.util import get_array
+
+
+def test_constructor_copy_input_interval_ea_default():
+    # GH 63388
+    arr = array([Interval(0, 1), Interval(1, 2)])
+    idx = IntervalIndex(arr)
+    assert not tm.shares_memory(arr, idx.array)
+
+
+def test_series_from_temporary_intervalindex_readonly_data():
+    # GH 63388
+    arr = array([Interval(0, 1), Interval(1, 2)])
+    arr._left.flags.writeable = False
+    arr._right.flags.writeable = False
+    ser = Series(IntervalIndex(arr))
+    assert not np.shares_memory(arr._left, get_array(ser)._left)
+    ser.iloc[0] = Interval(5, 6)
+    expected = Series(
+        [Interval(5, 6), Interval(1, 2)], 
+        dtype='interval[int64, right]'
+    )
+    tm.assert_series_equal(ser, expected)

From 122f554a2e84ce54cc72ac7b7b8a63e379b4f54b Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 08:11:10 -0600
Subject: [PATCH 11/30] ENH: Copy inputs in IntervalIndex constructor by
 default (GH#63388)

---
 pandas/core/indexes/interval.py | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index 7bb64503a469e..e6b7637f431fb 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -35,6 +35,7 @@
 )
 from pandas.util._exceptions import rewrite_exception
 
+from pandas.core.dtypes.astype import astype_is_view
 from pandas.core.dtypes.cast import (
     find_common_type,
     infer_dtype_from_scalar,
@@ -61,6 +62,7 @@
 from pandas.core.dtypes.missing import is_valid_na_for_dtype
 
 from pandas.core.algorithms import unique
+from pandas.core.arrays import ExtensionArray
 from pandas.core.arrays.datetimelike import validate_periods
 from pandas.core.arrays.interval import (
     IntervalArray,
@@ -169,8 +171,13 @@ class IntervalIndex(ExtensionIndex):
         neither.
     dtype : dtype or None, default None
         If None, dtype will be inferred.
-    copy : bool, default False
-        Copy the input data.
+    copy : bool, default None
+        Whether to copy input data, only relevant for array, Series, and Index
+        inputs (for other input, e.g. a list, a new array is created anyway).
+        Defaults to True for array input and False for Index/Series.
+        Set to False to avoid copying array input at your own risk (if you
+        know the input data won't be modified elsewhere).
+        Set to True to force copying Series/Index input up front.
     name : object, optional
          Name to be stored in the index.
     verify_integrity : bool, default True
@@ -252,12 +259,19 @@ def __new__(
         data,
         closed: IntervalClosedType | None = None,
         dtype: Dtype | None = None,
-        copy: bool = False,
+        copy: bool | None = None,
         name: Hashable | None = None,
         verify_integrity: bool = True,
     ) -> Self:
         name = maybe_extract_name(name, data, cls)
 
+        if isinstance(data, (ExtensionArray, np.ndarray)):
+            # GH#63388
+            if copy is not False:
+                if dtype is None or astype_is_view(data.dtype, dtype):
+                    data = data.copy()
+                    copy = False
+
         with rewrite_exception("IntervalArray", cls.__name__):
             array = IntervalArray(
                 data,

From 66a37fe1ea3b841f694d1d8f724621954076fdd9 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 08:17:29 -0600
Subject: [PATCH 12/30] STYLE: Apply isort fixes

---
 pandas/core/indexes/datetimes.py  | 4 ++--
 pandas/core/indexes/timedeltas.py | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index 21944a0e62c79..4bd8452e3657c 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -37,20 +37,20 @@
 )
 from pandas.util._exceptions import find_stack_level
 
+from pandas.core.dtypes.astype import astype_is_view
 from pandas.core.dtypes.common import is_scalar
 from pandas.core.dtypes.dtypes import (
     ArrowDtype,
     DatetimeTZDtype,
 )
-from pandas.core.dtypes.astype import astype_is_view
 from pandas.core.dtypes.generic import ABCSeries
 from pandas.core.dtypes.missing import is_valid_na_for_dtype
 
+from pandas.core.arrays import ExtensionArray
 from pandas.core.arrays.datetimes import (
     DatetimeArray,
     tz_to_dtype,
 )
-from pandas.core.arrays import ExtensionArray
 import pandas.core.common as com
 from pandas.core.indexes.base import (
     Index,
diff --git a/pandas/core/indexes/timedeltas.py b/pandas/core/indexes/timedeltas.py
index 15cf9b894e19e..811d637c73166 100644
--- a/pandas/core/indexes/timedeltas.py
+++ b/pandas/core/indexes/timedeltas.py
@@ -21,11 +21,11 @@
 from pandas._libs.tslibs.dtypes import abbrev_to_npy_unit
 from pandas.util._decorators import set_module
 
+from pandas.core.dtypes.astype import astype_is_view
 from pandas.core.dtypes.common import (
     is_scalar,
     pandas_dtype,
 )
-from pandas.core.dtypes.astype import astype_is_view
 from pandas.core.dtypes.dtypes import ArrowDtype
 from pandas.core.dtypes.generic import ABCSeries
 

From 5a211cc0767e6b9858810b53cfab7491fcbbb026 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 08:23:37 -0600
Subject: [PATCH 13/30] DOC: Add release note for GH#63388

---
 doc/source/whatsnew/v3.0.0.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/source/whatsnew/v3.0.0.rst b/doc/source/whatsnew/v3.0.0.rst
index a1de10f61306a..ce4e2d26e6270 100644
--- a/doc/source/whatsnew/v3.0.0.rst
+++ b/doc/source/whatsnew/v3.0.0.rst
@@ -820,6 +820,7 @@ Other API changes
   :meth:`~DataFrame.ffill`, :meth:`~DataFrame.bfill`, :meth:`~DataFrame.interpolate`,
   :meth:`~DataFrame.where`, :meth:`~DataFrame.mask`, :meth:`~DataFrame.clip`) now return
   the modified DataFrame or Series (``self``) instead of ``None`` when ``inplace=True`` (:issue:`63207`)
+- :class:`DatetimeIndex`, :class:`TimedeltaIndex`, :class:`PeriodIndex` and :class:`IntervalIndex` constructors now copy the input ``data`` by default when ``copy=None``, consistent with :class:`Index` behavior (:issue:`63388`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_300.deprecations:

From 937333304c890818660318afdf5e1e1592e44874 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 08:55:49 -0600
Subject: [PATCH 14/30] TYP: Fix mypy errors with type ignores

---
 pandas/core/indexes/datetimes.py | 6 ++++--
 pandas/core/indexes/interval.py  | 6 ++++--
 pandas/core/indexes/period.py    | 4 +++-
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index 4bd8452e3657c..1a395803a7f0a 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -689,7 +689,9 @@ def __new__(
         if isinstance(data, (ExtensionArray, np.ndarray)):
             # GH 63388
             if copy is not False:
-                if dtype is None or astype_is_view(data.dtype, dtype):
+                if dtype is None or astype_is_view(
+                    data.dtype, dtype # type: ignore[arg-type]
+                ): 
                     data = data.copy()
                     copy = False
 
@@ -708,7 +710,7 @@ def __new__(
         dtarr = DatetimeArray._from_sequence_not_strict(
             data,
             dtype=dtype,
-            copy=copy,
+            copy=bool(copy),
             tz=tz,
             freq=freq,
             dayfirst=dayfirst,
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index e6b7637f431fb..a2a74c4a7f4a7 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -268,7 +268,9 @@ def __new__(
         if isinstance(data, (ExtensionArray, np.ndarray)):
             # GH#63388
             if copy is not False:
-                if dtype is None or astype_is_view(data.dtype, dtype):
+                if dtype is None or astype_is_view(
+                    data.dtype, dtype # type: ignore[arg-type]
+                ):
                     data = data.copy()
                     copy = False
 
@@ -276,7 +278,7 @@ def __new__(
             array = IntervalArray(
                 data,
                 closed=closed,
-                copy=copy,
+                copy=bool(copy),
                 dtype=dtype,
                 verify_integrity=verify_integrity,
             )
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index 22118ae065aed..0b4e27f70d7c1 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -241,7 +241,9 @@ def __new__(
         if isinstance(data, (ExtensionArray, np.ndarray)):
             # GH 63388
             if copy is not False:
-                if dtype is None or astype_is_view(data.dtype, dtype):
+                if dtype is None or astype_is_view(
+                    data.dtype, dtype # type: ignore[arg-type]
+                ):
                     data = data.copy()
                     copy = False
 

From bc3c54af06a3ce033376d980ab3c72c0b6b3107f Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 08:58:27 -0600
Subject: [PATCH 15/30] TYP: Fix mypy errors using bool(copy) and ignores

---
 pandas/core/indexes/timedeltas.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/indexes/timedeltas.py b/pandas/core/indexes/timedeltas.py
index 811d637c73166..a92347feb407f 100644
--- a/pandas/core/indexes/timedeltas.py
+++ b/pandas/core/indexes/timedeltas.py
@@ -208,7 +208,7 @@ def __new__(
         # - Cases checked above all return/raise before reaching here - #
 
         tdarr = TimedeltaArray._from_sequence_not_strict(
-            data, freq=freq, unit=None, dtype=dtype, copy=copy
+            data, freq=freq, unit=None, dtype=dtype, copy=bool(copy)
         )
         refs = None
         if not copy and isinstance(data, (ABCSeries, Index)):

From 6731252b9bdcf331310c28e179cc31b047f15a52 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 09:14:19 -0600
Subject: [PATCH 16/30] STY: Apply pre-commit fixes

---
 pandas/core/indexes/datetimes.py                    |  5 +++--
 pandas/core/indexes/interval.py                     |  3 ++-
 pandas/core/indexes/period.py                       |  3 ++-
 pandas/tests/copy_view/index/test_datetimeindex.py  |  5 ++---
 pandas/tests/copy_view/index/test_intervalindex.py  |  7 ++-----
 pandas/tests/copy_view/index/test_periodindex.py    | 12 ++++++------
 pandas/tests/copy_view/index/test_timedeltaindex.py |  7 +++----
 7 files changed, 20 insertions(+), 22 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index 1a395803a7f0a..6fb8331aad9b4 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -690,8 +690,9 @@ def __new__(
             # GH 63388
             if copy is not False:
                 if dtype is None or astype_is_view(
-                    data.dtype, dtype # type: ignore[arg-type]
-                ): 
+                    data.dtype,
+                    dtype,  # type: ignore[arg-type]
+                ):
                     data = data.copy()
                     copy = False
 
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index a2a74c4a7f4a7..4d403e5a6704c 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -269,7 +269,8 @@ def __new__(
             # GH#63388
             if copy is not False:
                 if dtype is None or astype_is_view(
-                    data.dtype, dtype # type: ignore[arg-type]
+                    data.dtype,
+                    dtype,  # type: ignore[arg-type]
                 ):
                     data = data.copy()
                     copy = False
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index 0b4e27f70d7c1..b09dab44284aa 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -242,7 +242,8 @@ def __new__(
             # GH 63388
             if copy is not False:
                 if dtype is None or astype_is_view(
-                    data.dtype, dtype # type: ignore[arg-type]
+                    data.dtype,
+                    dtype,  # type: ignore[arg-type]
                 ):
                     data = data.copy()
                     copy = False
diff --git a/pandas/tests/copy_view/index/test_datetimeindex.py b/pandas/tests/copy_view/index/test_datetimeindex.py
index f223d6236e032..ddbff4bafdeff 100644
--- a/pandas/tests/copy_view/index/test_datetimeindex.py
+++ b/pandas/tests/copy_view/index/test_datetimeindex.py
@@ -5,8 +5,8 @@
     DatetimeIndex,
     Series,
     Timestamp,
+    array,
     date_range,
-    array
 )
 import pandas._testing as tm
 from pandas.tests.copy_view.util import get_array
@@ -81,7 +81,6 @@ def test_series_from_temporary_datetimeindex_readonly_data():
     assert not np.shares_memory(arr, get_array(ser))
     ser.iloc[0] = Timestamp("2020-01-01")
     expected = Series(
-        [Timestamp("2020-01-01"), Timestamp("2020-01-02")], 
-        dtype="datetime64[ns]"
+        [Timestamp("2020-01-01"), Timestamp("2020-01-02")], dtype="datetime64[ns]"
     )
     tm.assert_series_equal(ser, expected)
diff --git a/pandas/tests/copy_view/index/test_intervalindex.py b/pandas/tests/copy_view/index/test_intervalindex.py
index 630687dc0c102..d30415d05e4e4 100644
--- a/pandas/tests/copy_view/index/test_intervalindex.py
+++ b/pandas/tests/copy_view/index/test_intervalindex.py
@@ -1,9 +1,9 @@
 import numpy as np
 
 from pandas import (
+    Interval,
     IntervalIndex,
     Series,
-    Interval,
     array,
 )
 import pandas._testing as tm
@@ -25,8 +25,5 @@ def test_series_from_temporary_intervalindex_readonly_data():
     ser = Series(IntervalIndex(arr))
     assert not np.shares_memory(arr._left, get_array(ser)._left)
     ser.iloc[0] = Interval(5, 6)
-    expected = Series(
-        [Interval(5, 6), Interval(1, 2)], 
-        dtype='interval[int64, right]'
-    )
+    expected = Series([Interval(5, 6), Interval(1, 2)], dtype="interval[int64, right]")
     tm.assert_series_equal(ser, expected)
diff --git a/pandas/tests/copy_view/index/test_periodindex.py b/pandas/tests/copy_view/index/test_periodindex.py
index 29fce0fb6290b..5f741d123f4a8 100644
--- a/pandas/tests/copy_view/index/test_periodindex.py
+++ b/pandas/tests/copy_view/index/test_periodindex.py
@@ -5,8 +5,8 @@
     Period,
     PeriodIndex,
     Series,
+    array,
     period_range,
-    array
 )
 import pandas._testing as tm
 from pandas.tests.copy_view.util import get_array
@@ -28,20 +28,20 @@ def test_periodindex(box):
 
 def test_constructor_copy_input_period_ea_default():
     # GH 63388
-    arr = array(['2020-01-01', '2020-01-02'], dtype='period[D]')
+    arr = array(["2020-01-01", "2020-01-02"], dtype="period[D]")
     idx = PeriodIndex(arr)
     assert not tm.shares_memory(arr, idx.array)
 
 
 def test_series_from_temporary_periodindex_readonly_data():
     # GH 63388
-    arr = array(['2020-01-01', '2020-01-02'], dtype='period[D]')
+    arr = array(["2020-01-01", "2020-01-02"], dtype="period[D]")
     arr._ndarray.flags.writeable = False
     ser = Series(PeriodIndex(arr))
     assert not np.shares_memory(arr._ndarray, get_array(ser))
-    ser.iloc[0] = Period('2022-01-01', freq='D')
+    ser.iloc[0] = Period("2022-01-01", freq="D")
     expected = Series(
-        [Period('2022-01-01', freq='D'), Period('2020-01-02', freq='D')], 
-        dtype='period[D]'
+        [Period("2022-01-01", freq="D"), Period("2020-01-02", freq="D")],
+        dtype="period[D]",
     )
     tm.assert_series_equal(ser, expected)
diff --git a/pandas/tests/copy_view/index/test_timedeltaindex.py b/pandas/tests/copy_view/index/test_timedeltaindex.py
index 0888665e469eb..9f4dcc39fe6f6 100644
--- a/pandas/tests/copy_view/index/test_timedeltaindex.py
+++ b/pandas/tests/copy_view/index/test_timedeltaindex.py
@@ -5,8 +5,8 @@
     Series,
     Timedelta,
     TimedeltaIndex,
+    array,
     timedelta_range,
-    array
 )
 import pandas._testing as tm
 from pandas.tests.copy_view.util import get_array
@@ -49,12 +49,11 @@ def test_constructor_copy_input_timedelta_ea_default():
 def test_series_from_temporary_timedeltaindex_readonly_data():
     # GH 63388
     arr = np.array([1, 2], dtype="timedelta64[ns]")
-    arr.flags.writeable = False 
+    arr.flags.writeable = False
     ser = Series(TimedeltaIndex(arr))
     assert not np.shares_memory(arr, get_array(ser))
     ser.iloc[0] = Timedelta(days=1)
     expected = Series(
-        [Timedelta(days=1), Timedelta(nanoseconds=2)],
-        dtype="timedelta64[ns]"
+        [Timedelta(days=1), Timedelta(nanoseconds=2)], dtype="timedelta64[ns]"
     )
     tm.assert_series_equal(ser, expected)

From 9acc8d1d6f11916c1069273a433e8f984655a771 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 09:48:46 -0600
Subject: [PATCH 17/30] FIX: Update regression test for copy default

---
 pandas/tests/indexes/datetimes/test_constructors.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/tests/indexes/datetimes/test_constructors.py b/pandas/tests/indexes/datetimes/test_constructors.py
index 4aa4c81558fa9..06ef4c057b5cb 100644
--- a/pandas/tests/indexes/datetimes/test_constructors.py
+++ b/pandas/tests/indexes/datetimes/test_constructors.py
@@ -1138,7 +1138,7 @@ def test_index_cast_datetime64_other_units(self):
     def test_constructor_int64_nocopy(self):
         # GH#1624
         arr = np.arange(1000, dtype=np.int64)
-        index = DatetimeIndex(arr)
+        index = DatetimeIndex(arr, copy=False)
 
         arr[50:100] = -1
         assert (index.asi8[50:100] == -1).all()

From 180fa7ed1e16b307f4a907b57943ac0d686289a6 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 09:50:17 -0600
Subject: [PATCH 18/30] FIX: handle string dtypes

---
 pandas/core/indexes/datetimes.py  | 7 +++++--
 pandas/core/indexes/interval.py   | 2 +-
 pandas/core/indexes/period.py     | 7 +++++--
 pandas/core/indexes/timedeltas.py | 5 ++++-
 4 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index 6fb8331aad9b4..bb5d47efbbc36 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -38,7 +38,10 @@
 from pandas.util._exceptions import find_stack_level
 
 from pandas.core.dtypes.astype import astype_is_view
-from pandas.core.dtypes.common import is_scalar
+from pandas.core.dtypes.common import (
+    is_scalar,
+    pandas_dtype,
+)
 from pandas.core.dtypes.dtypes import (
     ArrowDtype,
     DatetimeTZDtype,
@@ -691,7 +694,7 @@ def __new__(
             if copy is not False:
                 if dtype is None or astype_is_view(
                     data.dtype,
-                    dtype,  # type: ignore[arg-type]
+                    pandas_dtype(dtype),  # type: ignore[arg-type]
                 ):
                     data = data.copy()
                     copy = False
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index 4d403e5a6704c..17aabd1f495ca 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -270,7 +270,7 @@ def __new__(
             if copy is not False:
                 if dtype is None or astype_is_view(
                     data.dtype,
-                    dtype,  # type: ignore[arg-type]
+                    pandas_dtype(dtype),  # type: ignore[arg-type]
                 ):
                     data = data.copy()
                     copy = False
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index b09dab44284aa..7308d82169cce 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -28,7 +28,10 @@
 )
 
 from pandas.core.dtypes.astype import astype_is_view
-from pandas.core.dtypes.common import is_integer
+from pandas.core.dtypes.common import (
+    is_integer,
+    pandas_dtype,
+)
 from pandas.core.dtypes.dtypes import PeriodDtype
 from pandas.core.dtypes.generic import ABCSeries
 from pandas.core.dtypes.missing import is_valid_na_for_dtype
@@ -243,7 +246,7 @@ def __new__(
             if copy is not False:
                 if dtype is None or astype_is_view(
                     data.dtype,
-                    dtype,  # type: ignore[arg-type]
+                    pandas_dtype(dtype),  # type: ignore[arg-type]
                 ):
                     data = data.copy()
                     copy = False
diff --git a/pandas/core/indexes/timedeltas.py b/pandas/core/indexes/timedeltas.py
index a92347feb407f..5a09cbd58cfc4 100644
--- a/pandas/core/indexes/timedeltas.py
+++ b/pandas/core/indexes/timedeltas.py
@@ -175,7 +175,10 @@ def __new__(
         if isinstance(data, (ExtensionArray, np.ndarray)):
             # GH 63388
             if copy is not False:
-                if dtype is None or astype_is_view(data.dtype, dtype):
+                if dtype is None or astype_is_view(
+                    data.dtype, 
+                    pandas_dtype(dtype),
+                ):
                     data = data.copy()
                     copy = False
 

From f7a00a46ca969eefc62cc2f5b2c047de2f024ce9 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 09:54:59 -0600
Subject: [PATCH 19/30] FIX: Update test_array_tz to use copy=False

---
 pandas/tests/arrays/test_datetimelike.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/tests/arrays/test_datetimelike.py b/pandas/tests/arrays/test_datetimelike.py
index 60a80f9af78c5..b4c6060b11403 100644
--- a/pandas/tests/arrays/test_datetimelike.py
+++ b/pandas/tests/arrays/test_datetimelike.py
@@ -707,7 +707,7 @@ def test_array_object_dtype(self, arr1d):
     def test_array_tz(self, arr1d):
         # GH#23524
         arr = arr1d
-        dti = self.index_cls(arr1d)
+        dti = self.index_cls(arr1d, copy=False)
         copy_false = None if np_version_gt2 else False
 
         expected = dti.asi8.view("M8[ns]")

From ca90c29343f37710669471d775e84f9f0d2bab2c Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 09:57:55 -0600
Subject: [PATCH 20/30] STY: apply pre-commit fixes

---
 pandas/core/indexes/timedeltas.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/indexes/timedeltas.py b/pandas/core/indexes/timedeltas.py
index 5a09cbd58cfc4..b5b9fd6b6d046 100644
--- a/pandas/core/indexes/timedeltas.py
+++ b/pandas/core/indexes/timedeltas.py
@@ -176,7 +176,7 @@ def __new__(
             # GH 63388
             if copy is not False:
                 if dtype is None or astype_is_view(
-                    data.dtype, 
+                    data.dtype,
                     pandas_dtype(dtype),
                 ):
                     data = data.copy()

From 75a3aac7aaa2a8e6bbcd05358a4183b603fcb345 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 10:03:01 -0600
Subject: [PATCH 21/30] CLN: Remove unused type ignores

---
 pandas/core/indexes/datetimes.py | 2 +-
 pandas/core/indexes/interval.py  | 2 +-
 pandas/core/indexes/period.py    | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index bb5d47efbbc36..f54547a9adba4 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -694,7 +694,7 @@ def __new__(
             if copy is not False:
                 if dtype is None or astype_is_view(
                     data.dtype,
-                    pandas_dtype(dtype),  # type: ignore[arg-type]
+                    pandas_dtype(dtype),
                 ):
                     data = data.copy()
                     copy = False
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index 17aabd1f495ca..82656826204e6 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -270,7 +270,7 @@ def __new__(
             if copy is not False:
                 if dtype is None or astype_is_view(
                     data.dtype,
-                    pandas_dtype(dtype),  # type: ignore[arg-type]
+                    pandas_dtype(dtype),
                 ):
                     data = data.copy()
                     copy = False
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index 7308d82169cce..88aed71e03f50 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -246,7 +246,7 @@ def __new__(
             if copy is not False:
                 if dtype is None or astype_is_view(
                     data.dtype,
-                    pandas_dtype(dtype),  # type: ignore[arg-type]
+                    pandas_dtype(dtype),
                 ):
                     data = data.copy()
                     copy = False

From e689f7bbb1deee030fb6f85366fa0b2e032b1bee Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 11:58:45 -0600
Subject: [PATCH 22/30] REF: Add Index._maybe_copy_input helper (GH#63388)

Extracts the copy/view validation logic into a shared classmethod on the base Index class, as requested during review.
---
 pandas/core/indexes/base.py | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 3239621468c5a..44df26f738e21 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -5196,6 +5196,19 @@ def _raise_scalar_data_error(cls, data):
             "was passed"
         )
 
+    @classmethod
+    def _maybe_copy_input(cls, data, copy, dtype):
+        """
+        Ensure that the input data is copied if necessary.
+        GH#63388
+        """
+        if isinstance(data, (ExtensionArray, np.ndarray)):
+            if copy is not False:
+                if dtype is None or astype_is_view(data.dtype, pandas_dtype(dtype)):
+                    data = data.copy()
+                    copy = False
+        return data, copy
+
     def _validate_fill_value(self, value):
         """
         Check if the value can be inserted into our array without casting,

From 65d80120823414be6d97e6af1af491cf7b3a3172 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Wed, 17 Dec 2025 11:59:14 -0600
Subject: [PATCH 23/30] REF: Use _maybe_copy_input in Index subclasses
 (GH#63388)

Updates DatetimeIndex, TimedeltaIndex, PeriodIndex, and IntervalIndex to use the shared validation logic, reducing code duplication.
---
 pandas/core/indexes/datetimes.py  | 14 ++------------
 pandas/core/indexes/interval.py   | 13 ++-----------
 pandas/core/indexes/period.py     | 14 ++------------
 pandas/core/indexes/timedeltas.py | 15 ++-------------
 4 files changed, 8 insertions(+), 48 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index f54547a9adba4..bebdcc4e84c1a 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -37,10 +37,8 @@
 )
 from pandas.util._exceptions import find_stack_level
 
-from pandas.core.dtypes.astype import astype_is_view
 from pandas.core.dtypes.common import (
     is_scalar,
-    pandas_dtype,
 )
 from pandas.core.dtypes.dtypes import (
     ArrowDtype,
@@ -49,7 +47,6 @@
 from pandas.core.dtypes.generic import ABCSeries
 from pandas.core.dtypes.missing import is_valid_na_for_dtype
 
-from pandas.core.arrays import ExtensionArray
 from pandas.core.arrays.datetimes import (
     DatetimeArray,
     tz_to_dtype,
@@ -689,15 +686,8 @@ def __new__(
 
         name = maybe_extract_name(name, data, cls)
 
-        if isinstance(data, (ExtensionArray, np.ndarray)):
-            # GH 63388
-            if copy is not False:
-                if dtype is None or astype_is_view(
-                    data.dtype,
-                    pandas_dtype(dtype),
-                ):
-                    data = data.copy()
-                    copy = False
+        # GH#63388
+        data, copy = cls._maybe_copy_input(data, copy, dtype)
 
         if (
             isinstance(data, DatetimeArray)
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index 82656826204e6..032a116f0b4b5 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -35,7 +35,6 @@
 )
 from pandas.util._exceptions import rewrite_exception
 
-from pandas.core.dtypes.astype import astype_is_view
 from pandas.core.dtypes.cast import (
     find_common_type,
     infer_dtype_from_scalar,
@@ -62,7 +61,6 @@
 from pandas.core.dtypes.missing import is_valid_na_for_dtype
 
 from pandas.core.algorithms import unique
-from pandas.core.arrays import ExtensionArray
 from pandas.core.arrays.datetimelike import validate_periods
 from pandas.core.arrays.interval import (
     IntervalArray,
@@ -265,15 +263,8 @@ def __new__(
     ) -> Self:
         name = maybe_extract_name(name, data, cls)
 
-        if isinstance(data, (ExtensionArray, np.ndarray)):
-            # GH#63388
-            if copy is not False:
-                if dtype is None or astype_is_view(
-                    data.dtype,
-                    pandas_dtype(dtype),
-                ):
-                    data = data.copy()
-                    copy = False
+        # GH#63388
+        data, copy = cls._maybe_copy_input(data, copy, dtype)
 
         with rewrite_exception("IntervalArray", cls.__name__):
             array = IntervalArray(
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index 88aed71e03f50..afe88d857733b 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -27,16 +27,13 @@
     set_module,
 )
 
-from pandas.core.dtypes.astype import astype_is_view
 from pandas.core.dtypes.common import (
     is_integer,
-    pandas_dtype,
 )
 from pandas.core.dtypes.dtypes import PeriodDtype
 from pandas.core.dtypes.generic import ABCSeries
 from pandas.core.dtypes.missing import is_valid_na_for_dtype
 
-from pandas.core.arrays import ExtensionArray
 from pandas.core.arrays.period import (
     PeriodArray,
     period_array,
@@ -241,15 +238,8 @@ def __new__(
 
         freq = validate_dtype_freq(dtype, freq)
 
-        if isinstance(data, (ExtensionArray, np.ndarray)):
-            # GH 63388
-            if copy is not False:
-                if dtype is None or astype_is_view(
-                    data.dtype,
-                    pandas_dtype(dtype),
-                ):
-                    data = data.copy()
-                    copy = False
+        # GH#63388
+        data, copy = cls._maybe_copy_input(data, copy, dtype)
 
         # PeriodIndex allow PeriodIndex(period_index, freq=different)
         # Let's not encourage that kind of behavior in PeriodArray.
diff --git a/pandas/core/indexes/timedeltas.py b/pandas/core/indexes/timedeltas.py
index b5b9fd6b6d046..a9e2e0eeb8a94 100644
--- a/pandas/core/indexes/timedeltas.py
+++ b/pandas/core/indexes/timedeltas.py
@@ -7,8 +7,6 @@
     cast,
 )
 
-import numpy as np
-
 from pandas._libs import (
     index as libindex,
     lib,
@@ -21,7 +19,6 @@
 from pandas._libs.tslibs.dtypes import abbrev_to_npy_unit
 from pandas.util._decorators import set_module
 
-from pandas.core.dtypes.astype import astype_is_view
 from pandas.core.dtypes.common import (
     is_scalar,
     pandas_dtype,
@@ -29,7 +26,6 @@
 from pandas.core.dtypes.dtypes import ArrowDtype
 from pandas.core.dtypes.generic import ABCSeries
 
-from pandas.core.arrays import ExtensionArray
 from pandas.core.arrays.timedeltas import TimedeltaArray
 import pandas.core.common as com
 from pandas.core.indexes.base import (
@@ -172,15 +168,8 @@ def __new__(
     ):
         name = maybe_extract_name(name, data, cls)
 
-        if isinstance(data, (ExtensionArray, np.ndarray)):
-            # GH 63388
-            if copy is not False:
-                if dtype is None or astype_is_view(
-                    data.dtype,
-                    pandas_dtype(dtype),
-                ):
-                    data = data.copy()
-                    copy = False
+        # GH#63388
+        data, copy = cls._maybe_copy_input(data, copy, dtype)
 
         if is_scalar(data):
             cls._raise_scalar_data_error(data)

From 05d49242787d97489d73385665e61428f8f24a99 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Thu, 18 Dec 2025 05:37:32 -0600
Subject: [PATCH 24/30] DOC: Update release note for GH#63388

Clarifies that only array/EA inputs are copied by default, as requested by reviewers.
---
 doc/source/whatsnew/v3.0.0.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v3.0.0.rst b/doc/source/whatsnew/v3.0.0.rst
index ce4e2d26e6270..b02ca87b0ff78 100644
--- a/doc/source/whatsnew/v3.0.0.rst
+++ b/doc/source/whatsnew/v3.0.0.rst
@@ -820,7 +820,7 @@ Other API changes
   :meth:`~DataFrame.ffill`, :meth:`~DataFrame.bfill`, :meth:`~DataFrame.interpolate`,
   :meth:`~DataFrame.where`, :meth:`~DataFrame.mask`, :meth:`~DataFrame.clip`) now return
   the modified DataFrame or Series (``self``) instead of ``None`` when ``inplace=True`` (:issue:`63207`)
-- :class:`DatetimeIndex`, :class:`TimedeltaIndex`, :class:`PeriodIndex` and :class:`IntervalIndex` constructors now copy the input ``data`` by default when ``copy=None``, consistent with :class:`Index` behavior (:issue:`63388`)
+- All Index constructors now copy ``numpy.ndarray`` and ``ExtensionArray`` inputs by default when ``copy=None``, consistent with :class:`Series` behavior (:issue:`63388`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_300.deprecations:

From 1e61eb68561af421416ae5552ac21a6abdcb1645 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Thu, 18 Dec 2025 05:42:48 -0600
Subject: [PATCH 25/30] REF: Rename copy helper to _maybe_copy_array_input and
 add type hints (GH#63388)

---
 pandas/core/indexes/base.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 44df26f738e21..5e50e1a535df9 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -5197,7 +5197,7 @@ def _raise_scalar_data_error(cls, data):
         )
 
     @classmethod
-    def _maybe_copy_input(cls, data, copy, dtype):
+    def _maybe_copy_array_input(cls, data, copy: bool | None, dtype) -> tuple[Any, bool]:
         """
         Ensure that the input data is copied if necessary.
         GH#63388

From 5e87eabaa5e119fb523315c1006d20ea5063e875 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Thu, 18 Dec 2025 05:47:02 -0600
Subject: [PATCH 26/30] REF: update to use renamed _maybe_copy_array_input
 classmethod (GH#63388)

---
 pandas/core/indexes/datetimes.py  | 2 +-
 pandas/core/indexes/interval.py   | 2 +-
 pandas/core/indexes/period.py     | 2 +-
 pandas/core/indexes/timedeltas.py | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index bebdcc4e84c1a..2edb714e786ab 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -687,7 +687,7 @@ def __new__(
         name = maybe_extract_name(name, data, cls)
 
         # GH#63388
-        data, copy = cls._maybe_copy_input(data, copy, dtype)
+        data, copy = cls._maybe_copy_array_input(data, copy, dtype)
 
         if (
             isinstance(data, DatetimeArray)
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index 032a116f0b4b5..3bf1357cfa68f 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -264,7 +264,7 @@ def __new__(
         name = maybe_extract_name(name, data, cls)
 
         # GH#63388
-        data, copy = cls._maybe_copy_input(data, copy, dtype)
+        data, copy = cls._maybe_copy_array_input(data, copy, dtype)
 
         with rewrite_exception("IntervalArray", cls.__name__):
             array = IntervalArray(
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index afe88d857733b..51869505d0dab 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -239,7 +239,7 @@ def __new__(
         freq = validate_dtype_freq(dtype, freq)
 
         # GH#63388
-        data, copy = cls._maybe_copy_input(data, copy, dtype)
+        data, copy = cls._maybe_copy_array_input(data, copy, dtype)
 
         # PeriodIndex allow PeriodIndex(period_index, freq=different)
         # Let's not encourage that kind of behavior in PeriodArray.
diff --git a/pandas/core/indexes/timedeltas.py b/pandas/core/indexes/timedeltas.py
index a9e2e0eeb8a94..25910a7b77de2 100644
--- a/pandas/core/indexes/timedeltas.py
+++ b/pandas/core/indexes/timedeltas.py
@@ -169,7 +169,7 @@ def __new__(
         name = maybe_extract_name(name, data, cls)
 
         # GH#63388
-        data, copy = cls._maybe_copy_input(data, copy, dtype)
+        data, copy = cls._maybe_copy_array_input(data, copy, dtype)
 
         if is_scalar(data):
             cls._raise_scalar_data_error(data)

From c290a305161bdd2e2a544373e1799964dd4e6c71 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Thu, 18 Dec 2025 05:53:29 -0600
Subject: [PATCH 27/30] REF: Return strict bool from copy helper and clean up
 call sites (GH#63388)

Updates _maybe_copy_array_input to return 'bool(copy)' ensuring strictly boolean output. Removes now-redundant bool() casts in subclass constructors.
---
 pandas/core/indexes/base.py       | 2 +-
 pandas/core/indexes/datetimes.py  | 2 +-
 pandas/core/indexes/interval.py   | 2 +-
 pandas/core/indexes/timedeltas.py | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 5e50e1a535df9..9a1b57a8a2b6a 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -5207,7 +5207,7 @@ def _maybe_copy_array_input(cls, data, copy: bool | None, dtype) -> tuple[Any, b
                 if dtype is None or astype_is_view(data.dtype, pandas_dtype(dtype)):
                     data = data.copy()
                     copy = False
-        return data, copy
+        return data, bool(copy)
 
     def _validate_fill_value(self, value):
         """
diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index 2edb714e786ab..a702549900213 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -704,7 +704,7 @@ def __new__(
         dtarr = DatetimeArray._from_sequence_not_strict(
             data,
             dtype=dtype,
-            copy=bool(copy),
+            copy=copy,
             tz=tz,
             freq=freq,
             dayfirst=dayfirst,
diff --git a/pandas/core/indexes/interval.py b/pandas/core/indexes/interval.py
index 3bf1357cfa68f..1def317bc1a88 100644
--- a/pandas/core/indexes/interval.py
+++ b/pandas/core/indexes/interval.py
@@ -270,7 +270,7 @@ def __new__(
             array = IntervalArray(
                 data,
                 closed=closed,
-                copy=bool(copy),
+                copy=copy,
                 dtype=dtype,
                 verify_integrity=verify_integrity,
             )
diff --git a/pandas/core/indexes/timedeltas.py b/pandas/core/indexes/timedeltas.py
index 25910a7b77de2..725ef8cae7120 100644
--- a/pandas/core/indexes/timedeltas.py
+++ b/pandas/core/indexes/timedeltas.py
@@ -200,7 +200,7 @@ def __new__(
         # - Cases checked above all return/raise before reaching here - #
 
         tdarr = TimedeltaArray._from_sequence_not_strict(
-            data, freq=freq, unit=None, dtype=dtype, copy=bool(copy)
+            data, freq=freq, unit=None, dtype=dtype, copy=copy
         )
         refs = None
         if not copy and isinstance(data, (ABCSeries, Index)):

From 02af4fb6b338385bebaa7783575d469ecfe25aa1 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Thu, 18 Dec 2025 05:59:04 -0600
Subject: [PATCH 28/30] STY: Revert import formatting (GH#63388)

---
 pandas/core/indexes/datetimes.py | 4 +---
 pandas/core/indexes/period.py    | 4 +---
 2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index a702549900213..72b009a344193 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -37,9 +37,7 @@
 )
 from pandas.util._exceptions import find_stack_level
 
-from pandas.core.dtypes.common import (
-    is_scalar,
-)
+from pandas.core.dtypes.common import is_scalar
 from pandas.core.dtypes.dtypes import (
     ArrowDtype,
     DatetimeTZDtype,
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index 51869505d0dab..b8a25ab0da693 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -27,9 +27,7 @@
     set_module,
 )
 
-from pandas.core.dtypes.common import (
-    is_integer,
-)
+from pandas.core.dtypes.common import is_integer
 from pandas.core.dtypes.dtypes import PeriodDtype
 from pandas.core.dtypes.generic import ABCSeries
 from pandas.core.dtypes.missing import is_valid_na_for_dtype

From e2b0f49dfcdab1e82f3094ea8036a656f4b2042e Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Thu, 18 Dec 2025 06:18:48 -0600
Subject: [PATCH 29/30] REF: Use copy helper for GH#63306 logic in Index
 constructor

---
 pandas/core/indexes/base.py | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 6fd3eb22aa78f..c7fc8633d03c3 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -505,12 +505,8 @@ def __new__(
         if not copy and isinstance(data, (ABCSeries, Index)):
             refs = data._references
 
-        if isinstance(data, (ExtensionArray, np.ndarray)):
-            # GH 63306
-            if copy is not False:
-                if dtype is None or astype_is_view(data.dtype, dtype):
-                    data = data.copy()
-                    copy = False
+        # GH 63306, GH 63388
+        data, copy = cls._maybe_copy_array_input(data, copy, dtype)
 
         # range
         if isinstance(data, (range, RangeIndex)):

From f8721aa858d9da729425f5900f717c58e275b353 Mon Sep 17 00:00:00 2001
From: zacharym-collins <colz5081@gmail.com>
Date: Thu, 18 Dec 2025 06:22:36 -0600
Subject: [PATCH 30/30] STY: Apply ruff formatting to method signature

---
 pandas/core/indexes/base.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index c7fc8633d03c3..ecfd26a412c2d 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -5194,7 +5194,9 @@ def _raise_scalar_data_error(cls, data):
         )
 
     @classmethod
-    def _maybe_copy_array_input(cls, data, copy: bool | None, dtype) -> tuple[Any, bool]:
+    def _maybe_copy_array_input(
+        cls, data, copy: bool | None, dtype
+    ) -> tuple[Any, bool]:
         """
         Ensure that the input data is copied if necessary.
         GH#63388