diff -r 55fa8e38a5f0 Modules/timemodule.c
--- a/Modules/timemodule.c	Wed Sep 14 10:26:20 2016 +0200
+++ b/Modules/timemodule.c	Wed Sep 14 14:34:51 2016 +0200
@@ -339,25 +339,38 @@
     return 1;
 }
 
+#ifdef MS_WINDOWS
+static struct tm *localtime_r(const time_t *timep, struct tm *result)
+{
+    if (localtime_s(result, timep) == 0)
+        return result;
+    return NULL;
+}
+static struct tm *gmtime_r(const time_t *timep, struct tm *result)
+{
+    if (gmtime_s(result, timep) == 0)
+        return result;
+    return NULL;
+}
+#endif
+
 static PyObject *
 time_gmtime(PyObject *self, PyObject *args)
 {
     time_t when;
-    struct tm buf, *local;
+    struct tm buf;
 
     if (!parse_time_t_args(args, "|O:gmtime", &when))
         return NULL;
 
     errno = 0;
-    local = gmtime(&when);
-    if (local == NULL) {
+    if (gmtime_r(&when, &buf) == NULL) {
 #ifdef EINVAL
         if (errno == 0)
             errno = EINVAL;
 #endif
         return PyErr_SetFromErrno(PyExc_OSError);
     }
-    buf = *local;
 #ifdef HAVE_STRUCT_TM_TM_ZONE
     return tmtotuple(&buf);
 #else
@@ -391,11 +404,8 @@
 static int
 pylocaltime(time_t *timep, struct tm *result)
 {
-    struct tm *local;
-
     assert (timep != NULL);
-    local = localtime(timep);
-    if (local == NULL) {
+    if (localtime_r(timep, result) == NULL) {
         /* unconvertible time */
 #ifdef EINVAL
         if (errno == 0)
@@ -404,7 +414,6 @@
         PyErr_SetFromErrno(PyExc_OSError);
         return -1;
     }
-    *result = *local;
     return 0;
 }
 
@@ -1239,18 +1248,18 @@
     {
 #define YEAR ((time_t)((365 * 24 + 6) * 3600))
         time_t t;
-        struct tm *p;
+        struct tm p;
         long janzone, julyzone;
         char janname[10], julyname[10];
         t = (time((time_t *)0) / YEAR) * YEAR;
-        p = localtime(&t);
-        get_zone(janname, 9, p);
-        janzone = -get_gmtoff(t, p);
+        localtime_r(&t, &p);
+        get_zone(janname, 9, &p);
+        janzone = -get_gmtoff(t, &p);
         janname[9] = '\0';
         t += YEAR/2;
-        p = localtime(&t);
-        get_zone(julyname, 9, p);
-        julyzone = -get_gmtoff(t, p);
+        localtime_r(&t, &p);
+        get_zone(julyname, 9, &p);
+        julyzone = -get_gmtoff(t, &p);
         julyname[9] = '\0';
 
         if( janzone < julyzone ) {