When getting the numpy datatype, return datetime64[D] for pa.Date32 and return datetime64[ms] for pa.Date64

doc/source/whatsnew/v3.0.0.rst

@@ -1108,6 +1108,7 @@ Numeric
 
 Conversion
 ^^^^^^^^^^
+- Bug in :meth:`ArrowDtype._get_common_dtype` and :meth:`ExtentionDtype._get_common_dtype` when using ``date32[pyarrow]`` and ``date64[pyarrow]`` types (:issue:`62343`)
 - Bug in :meth:`DataFrame.astype` not casting ``values`` for Arrow-based dictionary dtype correctly (:issue:`58479`)
 - Bug in :meth:`DataFrame.update` bool dtype being converted to object (:issue:`55509`)
 - Bug in :meth:`Series.astype` might modify read-only array inplace when casting to a string dtype (:issue:`57212`)

pandas/core/dtypes/dtypes.py

@@ -2277,6 +2277,18 @@ def name(self) -> str:  # type: ignore[override]
     @cache_readonly
     def numpy_dtype(self) -> np.dtype:
         """Return an instance of the related numpy dtype"""
+        if pa.types.is_date32(self.pyarrow_dtype):
+            # pa.timestamp(unit).to_pandas_dtype() returns ns units
+            # regardless of the pyarrow timestamp units.
+            # This can be removed if/when pyarrow addresses it:
+            # https://github.com/apache/arrow/issues/34462
+            return np.dtype("datetime64[D]")
+        if pa.types.is_date64(self.pyarrow_dtype):
+            # pa.timestamp(unit).to_pandas_dtype() returns ns units
+            # regardless of the pyarrow timestamp units.
+            # This can be removed if/when pyarrow addresses it:
+            # https://github.com/apache/arrow/issues/34462
+            return np.dtype("datetime64[ms]")
         if pa.types.is_timestamp(self.pyarrow_dtype):
             # pa.timestamp(unit).to_pandas_dtype() returns ns units
             # regardless of the pyarrow timestamp units.

pandas/tests/extension/test_arrow.py

@@ -650,7 +650,7 @@ def test_construct_from_string_another_type_raises(self, dtype):
     def test_get_common_dtype(self, dtype, request):
         pa_dtype = dtype.pyarrow_dtype
         if (
-            pa.types.is_date(pa_dtype)
+            pa.types.is_date64(pa_dtype)
             or pa.types.is_time(pa_dtype)
             or (pa.types.is_timestamp(pa_dtype) and pa_dtype.tz is not None)
             or pa.types.is_binary(pa_dtype)
@@ -1087,9 +1087,9 @@ def test_comp_masked_numpy(self, masked_dtype, comparison_op):
 
     def test_loc_setitem_with_expansion_preserves_ea_index_dtype(self, data, request):
         pa_dtype = data.dtype.pyarrow_dtype
-        if pa.types.is_date(pa_dtype):
+        if pa.types.is_date64(pa_dtype):
             mark = pytest.mark.xfail(
-                reason="GH#62343 incorrectly casts to timestamp[ms][pyarrow]"
+                reason="GH#62343 incorrectly casts date64 to timestamp[ms][pyarrow]"
             )
             request.applymarker(mark)
         super().test_loc_setitem_with_expansion_preserves_ea_index_dtype(data)