REGR: nanosecond timestamp comparisons to OOB datetimes (#42796)

Author: mzeitlin11

doc/source/whatsnew/v1.3.2.rst

@@ -19,6 +19,7 @@ Fixed regressions
 - Regression in :meth:`DataFrame.from_records` with empty records (:issue:`42456`)
 - Fixed regression in :meth:`DataFrame.shift` where TypeError occurred when shifting DataFrame created by concatenation of slices and fills with values (:issue:`42719`)
 - Regression in :meth:`DataFrame.agg` when the ``func`` argument returned lists and ``axis=1`` (:issue:`42727`)
+- Fixed regression in comparisons between :class:`Timestamp` object and ``datetime64`` objects outside the implementation bounds for nanosecond ``datetime64`` (:issue:`42794`)
 -
 
 .. ---------------------------------------------------------------------------

pandas/_libs/tslibs/timestamps.pyx

@@ -270,9 +270,9 @@ cdef class _Timestamp(ABCTimestamp):
         if op == Py_EQ:
             return False
         if op == Py_LE or op == Py_LT:
-            return other.year <= self.year
+            return self.year <= other.year
         if op == Py_GE or op == Py_GT:
-            return other.year >= self.year
+            return self.year >= other.year
 
     cdef bint _can_compare(self, datetime other):
         if self.tzinfo is not None:

pandas/tests/scalar/timestamp/test_comparisons.py

@@ -266,6 +266,19 @@ def test_timestamp_compare_oob_dt64(self):
         assert Timestamp.max < other + us
         # Note: numpy gets the reversed comparison wrong
 
+        # GH-42794
+        other = datetime(9999, 9, 9)
+        assert Timestamp.min < other
+        assert other > Timestamp.min
+        assert Timestamp.max < other
+        assert other > Timestamp.max
+
+        other = datetime(1, 1, 1)
+        assert Timestamp.max > other
+        assert other < Timestamp.max
+        assert Timestamp.min > other
+        assert other < Timestamp.min
+
     def test_compare_zerodim_array(self):
         # GH#26916
         ts = Timestamp.now()

pandas/tests/series/methods/test_clip.py

@@ -1,3 +1,5 @@
+from datetime import datetime
+
 import numpy as np
 import pytest
 
@@ -128,6 +130,15 @@ def test_clip_with_datetimes(self):
         )
         tm.assert_series_equal(result, expected)
 
+    def test_clip_with_timestamps_and_oob_datetimes(self):
+        # GH-42794
+        ser = Series([datetime(1, 1, 1), datetime(9999, 9, 9)])
+
+        result = ser.clip(lower=Timestamp.min, upper=Timestamp.max)
+        expected = Series([Timestamp.min, Timestamp.max], dtype="object")
+
+        tm.assert_series_equal(result, expected)
+
     def test_clip_pos_args_deprecation(self):
         # https://github.com/pandas-dev/pandas/issues/41485
         ser = Series([1, 2, 3])