Making to_datetime('today') and Timestamp('today') consistent (#19937)

Author: shangyian

doc/source/whatsnew/v0.23.0.txt

@@ -652,6 +652,7 @@ Other API Changes
 - Set operations (union, difference...) on :class:`IntervalIndex` with incompatible index types will now raise a ``TypeError`` rather than a ``ValueError`` (:issue:`19329`)
 - :class:`DateOffset` objects render more simply, e.g. ``<DateOffset: days=1>`` instead of ``<DateOffset: kwds={'days': 1}>`` (:issue:`19403`)
 - ``Categorical.fillna`` now validates its ``value`` and ``method`` keyword arguments. It now raises when both or none are specified, matching the behavior of :meth:`Series.fillna` (:issue:`19682`)
+- ``pd.to_datetime('today')`` now returns a datetime, consistent with ``pd.Timestamp('today')``; previously ``pd.to_datetime('today')`` returned a ``.normalized()`` datetime (:issue:`19935`)
 - :func:`Series.str.replace` now takes an optional `regex` keyword which, when set to ``False``, uses literal string replacement rather than regex replacement (:issue:`16808`)
 
 .. _whatsnew_0230.deprecations:

pandas/_libs/tslib.pyx

@@ -755,8 +755,7 @@ cdef inline bint _parse_today_now(str val, int64_t* iresult):
         iresult[0] = Timestamp.utcnow().value
         return True
     elif val == 'today':
-        # Note: this is *not* the same as Timestamp('today')
-        iresult[0] = Timestamp.now().normalize().value
+        iresult[0] = Timestamp.today().value
         return True
     return False
 

pandas/tests/indexes/datetimes/test_tools.py

@@ -224,27 +224,34 @@ def test_to_datetime_today(self):
         # 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]')
+            nptoday = np.datetime64('today')\
+                .astype('datetime64[ns]').astype(np.int64)
             pdtoday = pd.to_datetime('today')
             pdtoday2 = pd.to_datetime(['today'])[0]
 
+            tstoday = pd.Timestamp('today')
+            tstoday2 = pd.Timestamp.today()
+
             # These should all be equal with infinite perf; this gives
             # a generous margin of 10 seconds
-            assert abs(pdtoday.value - nptoday.astype(np.int64)) < 1e10
-            assert abs(pdtoday2.value - nptoday.astype(np.int64)) < 1e10
+            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]')
+            nptoday = np.datetime64('today')\
+                .astype('datetime64[ns]').astype(np.int64)
             pdtoday = pd.to_datetime('today')
             pdtoday2 = pd.to_datetime(['today'])[0]
 
             # These should all be equal with infinite perf; this gives
             # a generous margin of 10 seconds
-            assert abs(pdtoday.value - nptoday.astype(np.int64)) < 1e10
-            assert abs(pdtoday2.value - nptoday.astype(np.int64)) < 1e10
+            assert abs(pdtoday.normalize().value - nptoday) < 1e10
+            assert abs(pdtoday2.normalize().value - nptoday) < 1e10
 
             assert pdtoday.tzinfo is None
             assert pdtoday2.tzinfo is None