numpy · chiffa · Aug 20, 2015 · Aug 21, 2015 · Aug 5, 2015 · Aug 5, 2015
diff --git a/numpy/core/src/umath/loops.c.src b/numpy/core/src/umath/loops.c.src
@@ -1287,11 +1287,17 @@ TIMEDELTA_md_m_multiply(char **args, npy_intp *dimensions, npy_intp *steps, void
     BINARY_LOOP {
         const npy_timedelta in1 = *(npy_timedelta *)ip1;
         const double in2 = *(double *)ip2;
-        if (in1 == NPY_DATETIME_NAT || npy_isnan(in2)) {
+        if (in1 == NPY_DATETIME_NAT) {
             *((npy_timedelta *)op1) = NPY_DATETIME_NAT;
         }
         else {
-            *((npy_timedelta *)op1) = (npy_timedelta)(in1 * in2);
+            double result = in1 * in2;
+            if (npy_isfinite(result)) {
+                *((npy_timedelta *)op1) = (npy_timedelta)result;
+            }
+            else {
+                *((npy_timedelta *)op1) = NPY_DATETIME_NAT;
+            }
         }
     }
 }
@@ -1302,11 +1308,17 @@ TIMEDELTA_dm_m_multiply(char **args, npy_intp *dimensions, npy_intp *steps, void
     BINARY_LOOP {
         const double in1 = *(double *)ip1;
         const npy_timedelta in2 = *(npy_timedelta *)ip2;
-        if (npy_isnan(in1) || in2 == NPY_DATETIME_NAT) {
+        if (in2 == NPY_DATETIME_NAT) {
             *((npy_timedelta *)op1) = NPY_DATETIME_NAT;
         }
         else {
-            *((npy_timedelta *)op1) = (npy_timedelta)(in1 * in2);
+            double result = in1 * in2;
+            if (npy_isfinite(result)) {
+                *((npy_timedelta *)op1) = (npy_timedelta)result;
+            }
+            else {
+                *((npy_timedelta *)op1) = NPY_DATETIME_NAT;
+            }
         }
     }
 }
@@ -1338,11 +1350,11 @@ TIMEDELTA_md_m_divide(char **args, npy_intp *dimensions, npy_intp *steps, void *
         }
         else {
             double result = in1 / in2;
-            if (npy_isnan(result)) {
-                *((npy_timedelta *)op1) = NPY_DATETIME_NAT;
+            if (npy_isfinite(result)) {
+                *((npy_timedelta *)op1) = (npy_timedelta)result;
             }
             else {
-                *((npy_timedelta *)op1) = (npy_timedelta)(result);
+                *((npy_timedelta *)op1) = NPY_DATETIME_NAT;
             }
         }
     }

diff --git a/numpy/core/tests/test_datetime.py b/numpy/core/tests/test_datetime.py
@@ -1,6 +1,7 @@
 from __future__ import division, absolute_import, print_function
 
 import pickle
+import warnings
 
 import numpy
 import numpy as np
@@ -961,6 +962,21 @@ def test_datetime_multiply(self):
             # float * M8
             assert_raises(TypeError, np.multiply, 1.5, dta)
 
+        # NaTs
+        with warnings.catch_warnings():
+            warnings.filterwarnings('ignore', category=RuntimeWarning)
+            nat = np.timedelta64('NaT')
+            def check(a, b, res):
+                assert_equal(a * b, res)
+                assert_equal(b * a, res)
+            for tp in (int, float):
+                check(nat, tp(2), nat)
+                check(nat, tp(0), nat)
+            for f in (float('inf'), float('nan')):
+                check(np.timedelta64(1), f, nat)
+                check(np.timedelta64(0), f, nat)
+                check(nat, f, nat)
+
     def test_datetime_divide(self):
         for dta, tda, tdb, tdc, tdd in \
                     [
@@ -1010,6 +1026,24 @@ def test_datetime_divide(self):
             # float / M8
             assert_raises(TypeError, np.divide, 1.5, dta)
 
+        # NaTs
+        with warnings.catch_warnings():
+            warnings.filterwarnings('ignore', category=RuntimeWarning)
+            nat = np.timedelta64('NaT')
+            for tp in (int, float):
+                assert_equal(np.timedelta64(1) / tp(0), nat)
+                assert_equal(np.timedelta64(0) / tp(0), nat)
+                assert_equal(nat / tp(0), nat)
+                assert_equal(nat / tp(2), nat)
+            # Division by inf
+            assert_equal(np.timedelta64(1) / float('inf'), np.timedelta64(0))
+            assert_equal(np.timedelta64(0) / float('inf'), np.timedelta64(0))
+            assert_equal(nat / float('inf'), nat)
+            # Division by nan
+            assert_equal(np.timedelta64(1) / float('nan'), nat)
+            assert_equal(np.timedelta64(0) / float('nan'), nat)
+            assert_equal(nat / float('nan'), nat)
+
     def test_datetime_compare(self):
         # Test all the comparison operators
         a = np.datetime64('2000-03-12T18:00:00.000000-0600')