BUG: to_datetime re-parsing Arrow-backed objects

pandas/core/tools/datetimes.py

@@ -57,7 +57,10 @@
  is_list_like,
  is_numeric_dtype,
 )
-from pandas.core.dtypes.dtypes import DatetimeTZDtype
+from pandas.core.dtypes.dtypes import (
+ ArrowDtype,
+ DatetimeTZDtype,
+)
 from pandas.core.dtypes.generic import (
  ABCDataFrame,
  ABCSeries,
@@ -400,6 +403,18 @@ def _convert_listlike_datetimes(
  arg = arg.tz_convert(None).tz_localize("utc")
  return arg
 
+ elif isinstance(arg_dtype, ArrowDtype) and np.issubdtype(
+ arg_dtype.numpy_dtype, np.datetime64
+ ):
+ # TODO: Combine with above if DTI/DTA supports Arrow timestamps
+ if utc:
+ import pyarrow as pa
+
+ # array attribute has to exist since arg is Index/Series at this point
+ arg_arr = arg.array._pa_array
+ arg._pa_array = arg_arr.cast(pa.timestamp(arg_arr.type.unit, "utc"))
+ return arg
+
  elif lib.is_np_dtype(arg_dtype, "M"):
  arg_dtype = cast(np.dtype, arg_dtype)
  if not is_supported_unit(get_unit_from_dtype(arg_dtype)):

pandas/tests/tools/test_to_datetime.py

@@ -933,6 +933,20 @@ def test_to_datetime_dtarr(self, tz):
  result = to_datetime(arr)
  assert result is arr
 
+ @td.skip_if_no("pyarrow")
+ @pytest.mark.parametrize("utc", [True, False])
+ @pytest.mark.parametrize("tz", [None, "US/Central"])
+ def test_to_datetime_arrow(self, tz, utc):
+ import pyarrow as pa
+
+ dti = date_range("1965-04-03", periods=19, freq="2W", tz=tz)
+ dti_arrow = dti.astype(pd.ArrowDtype(pa.timestamp(unit="ns")))
+
+ result = to_datetime(dti_arrow, utc=utc)
+ expected = to_datetime(dti, utc=utc).astype("timestamp[ns][pyarrow]")
+ assert result is dti_arrow
+ tm.assert_index_equal(result, expected, exact=False)
+
  def test_to_datetime_pydatetime(self):
  actual = to_datetime(datetime(2008, 1, 15))
  assert actual == datetime(2008, 1, 15)