Check to_datetime("now") and to_datetime("today")

According to pandas-devGH-18705 to_datetime("now") and to_datetime("today")
must match semantics of Timestamp.now() and Timestamp.today().

Author: miccoli

pandas/tests/tools/test_to_datetime.py

@@ -544,63 +544,36 @@ def test_to_datetime_unparseable_ignore(self):
 
     @td.skip_if_windows  # `tm.set_timezone` does not work in windows
     def test_to_datetime_now(self):
-        # See GH#18666
+        # See GH#18705, to_datetime("now") matches Timestamp.now()
         with tm.set_timezone("US/Eastern"):
-            npnow = np.datetime64("now").astype("datetime64[ns]")
+            tsnow = Timestamp.now()
             pdnow = to_datetime("now")
             pdnow2 = to_datetime(["now"])[0]
 
             # These should all be equal with infinite perf; this gives
-            # a generous margin of 10 seconds
-            assert abs(pdnow.value - npnow.astype(np.int64)) < 1e10
-            assert abs(pdnow2.value - npnow.astype(np.int64)) < 1e10
+            # a generous margin of 1 seconds
+            assert abs(pdnow.value - tsnow.value) < 1e9
+            assert abs(pdnow2.value - tsnow.value) < 1e9
 
             assert pdnow.tzinfo is None
             assert pdnow2.tzinfo is None
 
     @td.skip_if_windows  # `tm.set_timezone` does not work in windows
     def test_to_datetime_today(self):
-        # See GH#18666
-        # Test with one timezone far ahead of UTC and another far behind, so
-        # one of these will _almost_ always be in a different day from UTC.
-        # Unfortunately this test between 12 and 1 AM Samoa time
-        # this both of these timezones _and_ UTC will all be in the same day,
-        # so this test will not detect the regression introduced in #18666.
-        with tm.set_timezone("Pacific/Auckland"):  # 12-13 hours ahead of UTC
-            nptoday = np.datetime64("today").astype("datetime64[ns]").astype(np.int64)
-            pdtoday = to_datetime("today")
-            pdtoday2 = to_datetime(["today"])[0]
-
-            tstoday = Timestamp("today")
-            tstoday2 = Timestamp.today()
-
-            # These should all be equal with infinite perf; this gives
-            # a generous margin of 10 seconds
-            assert abs(pdtoday.normalize().value - nptoday) < 1e10
-            assert abs(pdtoday2.normalize().value - nptoday) < 1e10
-            assert abs(pdtoday.value - tstoday.value) < 1e10
-            assert abs(pdtoday.value - tstoday2.value) < 1e10
-
-            assert pdtoday.tzinfo is None
-            assert pdtoday2.tzinfo is None
-
-        with tm.set_timezone("US/Samoa"):  # 11 hours behind UTC
-            nptoday = np.datetime64("today").astype("datetime64[ns]").astype(np.int64)
+        # See GH##18705, to_datetime("today") matches Timestamp.today()
+        with tm.set_timezone("Pacific/Auckland"):
+            tstoday = Timestamp.today()
             pdtoday = to_datetime("today")
             pdtoday2 = to_datetime(["today"])[0]
 
             # These should all be equal with infinite perf; this gives
-            # a generous margin of 10 seconds
-            assert abs(pdtoday.normalize().value - nptoday) < 1e10
-            assert abs(pdtoday2.normalize().value - nptoday) < 1e10
+            # a generous margin of 1 seconds
+            assert abs(pdtoday.value - tstoday.value) < 1e9
+            assert abs(pdtoday2.value - tstoday.value) < 1e9
 
             assert pdtoday.tzinfo is None
             assert pdtoday2.tzinfo is None
 
-    def test_to_datetime_today_now_unicode_bytes(self):
-        to_datetime(["now"])
-        to_datetime(["today"])
-
     @pytest.mark.parametrize("cache", [True, False])
     def test_to_datetime_dt64s(self, cache):
         in_bound_dts = [np.datetime64("2000-01-01"), np.datetime64("2000-01-02")]