BUG: Fix tz_localize(None) with Arrow timestamp (#62076)

Author: yuanx749

doc/source/whatsnew/v3.0.0.rst

@@ -732,6 +732,7 @@ Timedelta
 Timezones
 ^^^^^^^^^
 - Bug in :meth:`DatetimeIndex.union`, :meth:`DatetimeIndex.intersection`, and :meth:`DatetimeIndex.symmetric_difference` changing timezone to UTC when merging two DatetimeIndex objects with the same timezone but different units (:issue:`60080`)
+- Bug in :meth:`Series.dt.tz_localize` with a timezone-aware :class:`ArrowDtype` incorrectly converting to UTC when ``tz=None`` (:issue:`61780`)
 -
 
 Numeric

pandas/core/arrays/arrow/array.py

@@ -2953,7 +2953,7 @@ def _dt_tz_localize(
         if nonexistent_pa is None:
             raise NotImplementedError(f"{nonexistent=} is not supported")
         if tz is None:
-            result = self._pa_array.cast(pa.timestamp(self.dtype.pyarrow_dtype.unit))
+            result = pc.local_timestamp(self._pa_array)
         else:
             result = pc.assume_timezone(
                 self._pa_array, str(tz), ambiguous=ambiguous, nonexistent=nonexistent_pa

pandas/tests/extension/test_arrow.py

@@ -2679,8 +2679,9 @@ def test_dt_tz_localize_unsupported_tz_options():
         ser.dt.tz_localize("UTC", nonexistent="NaT")
 
 
-@pytest.mark.xfail(reason="Converts to UTC before localizing GH#61780")
-def test_dt_tz_localize_none():
+def test_dt_tz_localize_none(request):
+    _require_timezone_database(request)
+
     ser = pd.Series(
         [datetime(year=2023, month=1, day=2, hour=3), None],
         dtype=ArrowDtype(pa.timestamp("ns", tz="US/Pacific")),