Issue #23517: datetime.datetime.fromtimestamp() and

datetime.datetime.utcfromtimestamp() now rounds to nearest with ties going away
from zero, instead of rounding towards minus infinity (-inf), as Python 2 and
Python older than 3.3.

Modules/_datetimemodule.c

@@ -4098,7 +4098,7 @@ datetime_from_timestamp(PyObject *cls, TM_FUNC f, PyObject *timestamp,
     long us;
 
     if (_PyTime_ObjectToTimeval(timestamp,
-                                &timet, &us, _PyTime_ROUND_FLOOR) == -1)
+                                &timet, &us, _PyTime_ROUND_HALF_UP) == -1)
         return NULL;
 
     return datetime_from_timet_and_us(cls, f, timet, (int)us, tzinfo);