Issue #23517: fromtimestamp() and utcfromtimestamp() methods of

datetime.datetime now round microseconds to nearest with ties going away from
zero (ROUND_HALF_UP), as Python 2 and Python older than 3.3, instead of
rounding towards -Infinity (ROUND_FLOOR).

Modules/_datetimemodule.c

@@ -4078,7 +4078,7 @@ 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);