Backport PR #55072 on branch 2.1.x (BUG: dt.tz with ArrowDtype returned string) (#55124)

Backport PR #55072: BUG: dt.tz with ArrowDtype returned string

Co-authored-by: Matthew Roeschke <[email protected]>

Author: meeseeksmachine

doc/source/whatsnew/v2.1.1.rst

@@ -35,6 +35,7 @@ Bug fixes
 ~~~~~~~~~
 - Fixed bug for :class:`ArrowDtype` raising ``NotImplementedError`` for fixed-size list (:issue:`55000`)
 - Fixed bug in :meth:`DataFrame.stack` with ``future_stack=True`` and columns a non-:class:`MultiIndex` consisting of tuples (:issue:`54948`)
+- Fixed bug in :meth:`Series.dt.tz` with :class:`ArrowDtype` where a string was returned instead of a ``tzinfo`` object (:issue:`55003`)
 - Fixed bug in :meth:`Series.pct_change` and :meth:`DataFrame.pct_change` showing unnecessary ``FutureWarning`` (:issue:`54981`)
 
 .. ---------------------------------------------------------------------------

pandas/core/arrays/arrow/array.py

@@ -18,6 +18,7 @@
 from pandas._libs.tslibs import (
     Timedelta,
     Timestamp,
+    timezones,
 )
 from pandas.compat import (
     pa_version_under7p0,
@@ -2421,7 +2422,7 @@ def _dt_time(self):
 
     @property
     def _dt_tz(self):
-        return self.dtype.pyarrow_dtype.tz
+        return timezones.maybe_get_tz(self.dtype.pyarrow_dtype.tz)
 
     @property
     def _dt_unit(self):

pandas/tests/extension/test_arrow.py

@@ -31,6 +31,7 @@
 import pytest
 
 from pandas._libs import lib
+from pandas._libs.tslibs import timezones
 from pandas.compat import (
     PY311,
     is_ci_environment,
@@ -2477,7 +2478,7 @@ def test_dt_tz(tz):
         dtype=ArrowDtype(pa.timestamp("ns", tz=tz)),
     )
     result = ser.dt.tz
-    assert result == tz
+    assert result == timezones.maybe_get_tz(tz)
 
 
 def test_dt_isocalendar():