BUG #31793 subtract datetime from Timestamp

Author: AnjoMan

pandas/_libs/tslibs/timestamps.pyx

@@ -368,9 +368,13 @@ cdef class _Timestamp(ABCTimestamp):
                 self = type(other)(self)
 
             # validate tz's
-            if not tz_compare(self.tzinfo, other.tzinfo):
-                raise TypeError("Timestamp subtraction must have the "
-                                "same timezones or no timezones")
+            naive_timezones = [
+                el.tzinfo is None or el.tzinfo.utcoffset(el) is None
+                for el in (self, other)
+            ]
+            if any(naive_timezones) and not all(naive_timezones):
+                raise TypeError("Cannot compute time difference between"
+                                " timezone-aware and naive datetime values.")
 
             # scalar Timestamp/datetime - Timestamp/datetime -> yields a
             # Timedelta

pandas/tests/tslibs/test_timedeltas.py

@@ -3,7 +3,7 @@
 
 from pandas._libs.tslibs.timedeltas import delta_to_nanoseconds
 
-from pandas import Timedelta, offsets
+from pandas import Timedelta, offsets, Timestamp
 
 
 @pytest.mark.parametrize(
@@ -34,3 +34,41 @@ def test_huge_nanoseconds_overflow():
     # GH 32402
     assert delta_to_nanoseconds(Timedelta(1e10)) == 1e10
     assert delta_to_nanoseconds(Timedelta(nanoseconds=1e10)) == 1e10
+
+
+class TestComputingDeltasWithTimezoneDifferences:
+    def test_fails_to_subtract_when_one_date_is_naive(self):
+        time1 = Timestamp("2020-10-28 22:08:00-04:00")
+        time2 = Timestamp("2020-10-28 22:08:00")
+
+        msg = (
+            "Cannot compute time difference between "
+            "timezone-aware and naive datetime values."
+        )
+        with pytest.raises(TypeError, match=msg):
+            time1 - time2
+
+        with pytest.raises(TypeError, match=msg):
+            time2 - time1
+
+    def test_subtracts_dates_of_different_timezones(self):
+        time1 = Timestamp("2020-10-28 22:08:00-04:00")
+        time2 = Timestamp("2020-10-28 22:08:00-00:00")
+
+        assert time1 - time2 == Timedelta("0 days 04:00:00")
+
+    def test_subtracts_dates_of_different_types(self):
+        """ Github issue 31793 """
+
+        time1 = Timestamp("2020-10-28 22:08:00-04:00")
+        time2 = Timestamp("2020-10-28 22:08:00-00:00").to_pydatetime()
+
+        assert time1 - time2 == Timedelta("0 days 04:00:00")
+        assert time2 - time1 == Timedelta("-1 days +20:00:00")
+
+    def test_subtracts_dates_that_are_both_naive(self):
+        time1 = Timestamp("2020-10-28 22:08:00")
+        time2 = Timestamp("2020-10-28 22:29:00")
+
+        assert time1 - time2 == Timedelta("-21 minutes")
+        assert time2 - time1 == Timedelta("21 minutes")