diff --git a/Lib/_pydatetime.py b/Lib/_pydatetime.py
index 26bcd1e491d78c..606ca79f34e13f 100644
--- a/Lib/_pydatetime.py
+++ b/Lib/_pydatetime.py
@@ -1989,7 +1989,11 @@ def _mktime(self):
         t = (self - epoch) // timedelta(0, 1)
         def local(u):
             y, m, d, hh, mm, ss = _time.localtime(u)[:6]
-            return (datetime(y, m, d, hh, mm, ss) - epoch) // timedelta(0, 1)
+            try:
+                return ((datetime(y, m, d, hh, mm, ss) - epoch) //
+                        timedelta(0, 1))
+            except (ValueError, OverflowError):
+                return u
 
         # Our goal is to solve t = local(u) for u.
         a = local(t) - t
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index 84eb872f964ba1..789ad16f8f7a3b 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -3122,6 +3122,18 @@ def dst(self, dt): return 1
         with self.assertRaises(TypeError):
             dt_broken.astimezone()
 
+        dt_big = self.theclass(9999, 12, 31, 23, 59, 59)
+        dt_big_utc = dt_big.replace(hour=19,
+                                    tzinfo=timezone(timedelta(hours=-4), 'EDT'))
+        self.assertEqual(dt_big_utc,
+                         dt_big.replace(tzinfo=timezone.utc).astimezone())
+
+        other_tz = timezone(timedelta(hours=+4), '+04')
+        dt_other_tz = dt_big.replace(tzinfo=other_tz)
+        dt_utc_tz = dt_big.replace(tzinfo=timezone.utc)
+        self.assertEqual(dt_other_tz, dt_other_tz.astimezone(tz=other_tz))
+        self.assertEqual(dt_utc_tz, dt_utc_tz.astimezone(tz=timezone.utc))
+
     def test_subclass_datetime(self):
 
         class C(self.theclass):
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 83b92fe606984c..accfc1bb1fcf49 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -5415,6 +5415,7 @@ local(long long u)
 {
     struct tm local_time;
     time_t t;
+    long long old_u = u;
     u -= epoch;
     t = u;
     if (t != u) {
@@ -5424,7 +5425,14 @@ local(long long u)
     }
     if (_PyTime_localtime(t, &local_time) != 0)
         return -1;
-    return utc_to_seconds(local_time.tm_year + 1900,
+
+    // Check edge cases
+    int year = local_time.tm_year + 1900;
+    if (year < MINYEAR || year > MAXYEAR) {
+        Py_DECREF(year);
+        return old_u;
+    }
+    return utc_to_seconds(year,
                           local_time.tm_mon + 1,
                           local_time.tm_mday,
                           local_time.tm_hour,