diff -r 7937aa6b7e92 Lib/test/test_time.py
--- a/Lib/test/test_time.py	Tue Jul 03 13:18:30 2012 +0200
+++ b/Lib/test/test_time.py	Tue Jul 03 11:00:46 2012 -0430
@@ -301,6 +301,72 @@
                 del environ['TZ']
             time.tzset()
 
+    def test_timezone_consistency(self):
+        from os import environ
+
+        org_TZ = environ.get('TZ',None)
+        try:
+            environ['TZ'] = 'GMT+0'
+            time.tzset()
+            uts = time.mktime(time.localtime())
+            # http://www.timeanddate.com/worldclock/difference.html?p1=58
+            tzones = [
+                ('America/New_York', 18000, 14400),
+                ('America/Chicago', 21600, 18000),
+                ('America/Los_Angeles', 28800, 52200),
+                ('America/Toronto', 18000, 14400),
+                ('CET', -3600, -3600),
+                ('CET-2CEST', -3600, -7200),
+                ('EST', 18000, 14400),
+                ('EST4EDT', 18000, 14400),
+                ('CST6CDT', 21600, 18000),
+                ('PST7PDT', 28800, 25200),
+                ('UTC', 0, 0),
+                ('Europe/London', 0, 3600),
+                ('Europe/Amsterdam', -3600, 7200),
+                ('Europe/Kiev', -7200, -7200),
+                ('Brazil/East', 10800, 10800),
+                ('Brazil/West', 14400, 1400),
+                ('VET4:30', 16200, 16200),
+                ('GMT+4:30', 16200, 16200),
+                ('Europe/Moscow', -14400, -14400),
+                ('America/Caracas', 16200, 16200)
+                ]
+
+            for tz, diff, dst in tzones:
+                environ['TZ'] = tz
+                time.tzset()
+
+                self.assertIsNotNone(time.tzname, tz)
+                self.assertIn(time.timezone, [diff, dst], time.tzname)
+
+                lts = time.mktime(time.gmtime()) - time.timezone
+                self.assertEqual(lts, uts, tz)
+               
+            # Show that time.timezone should not be used for calculations
+            # involving dates in the past. 
+            for tz, _s, _d in tzones:
+                environ['TZ'] = tz
+                time.tzset()
+                fmt = '%Y/%m/%d %H:%M:%S %Z'
+                bt = time.mktime(time.strptime('1969/7/20 20:18:00 UTC', fmt))
+                # note that strptime ignores the timezone and always
+                # parses as a local time
+                lbt = time.mktime(time.localtime(bt))
+                self.assertEqual(lbt, bt, tz)
+
+                ubt = time.mktime(time.gmtime(bt))
+                self.assertEqual(ubt, bt + time.timezone, tz)
+        finally:
+            # Repair TZ environment variable in case any other tests
+            # rely on it.
+            if org_TZ is not None:
+                environ['TZ'] = org_TZ
+            elif 'TZ' in environ:
+                del environ['TZ']
+            time.tzset()
+
+
     def test_insane_timestamps(self):
         # It's possible that some platform maps time_t to double,
         # and that this test will fail there.  This test should
diff -r 7937aa6b7e92 Misc/ACKS
--- a/Misc/ACKS	Tue Jul 03 13:18:30 2012 +0200
+++ b/Misc/ACKS	Tue Jul 03 11:00:46 2012 -0430
@@ -1167,3 +1167,4 @@
 Kai Zhu
 Tarek Ziadé
 Peter Åstrand
+Juancarlo Añez