Bug: Fix convert_dtypes not preserving timezone details for ArrowDtype

doc/source/whatsnew/v3.0.0.rst

@@ -671,6 +671,7 @@ Conversion
 - 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`)
 - Bug in :meth:`Series.reindex` not maintaining ``float32`` type when a ``reindex`` introduces a missing value (:issue:`45857`)
+- Bug in :meth:`convert_dtypes` not preserving timezone details for ArrowDtype in Series and DataFrame (:issue:`60237`)
 
 Strings
 ^^^^^^^

pandas/core/dtypes/cast.py

@@ -1113,7 +1113,7 @@ def convert_dtypes(
     else:
         inferred_dtype = input_array.dtype
 
-    if dtype_backend == "pyarrow":
+    if dtype_backend == "pyarrow" and not isinstance(inferred_dtype, ArrowDtype):
         from pandas.core.arrays.arrow.array import to_pyarrow_type
         from pandas.core.arrays.string_ import StringDtype
 

pandas/tests/extension/test_arrow.py

@@ -3511,3 +3511,27 @@ def test_map_numeric_na_action():
     result = ser.map(lambda x: 42, na_action="ignore")
     expected = pd.Series([42.0, 42.0, np.nan], dtype="float64")
     tm.assert_series_equal(result, expected)
+
+
+def test_convert_dtype_pyarrow_timezone_preserve():
+    # GH 60237
+    pytest.importorskip("pyarrow")
+    ser = pd.Series(
+        pd.to_datetime(range(5), utc=True, unit="h"),
+        dtype="timestamp[ns, tz=UTC][pyarrow]",
+    )
+    result = ser.convert_dtypes(dtype_backend="pyarrow")
+    expected = ser.copy()
+    tm.assert_series_equal(result, expected)
+
+    df = pd.DataFrame(
+        {
+            "timestamps": pd.Series(
+                pd.to_datetime(range(5), utc=True, unit="h"),
+                dtype="timestamp[ns, tz=UTC][pyarrow]",
+            )
+        }
+    )
+    result = df.convert_dtypes(dtype_backend="pyarrow")
+    expected = df.copy()
+    tm.assert_frame_equal(result, expected)