diff --git a/Lib/email/_parseaddr.py b/Lib/email/_parseaddr.py
index a2957572817..79573c61778 100644
--- a/Lib/email/_parseaddr.py
+++ b/Lib/email/_parseaddr.py
@@ -13,7 +13,7 @@ __all__ = [
     'quote',
     ]
 
-import time
+import time, calendar
 
 SPACE = ' '
 EMPTYSTRING = ''
@@ -152,13 +152,13 @@ def parsedate(data):
 
 
 def mktime_tz(data):
-    """Turn a 10-tuple as returned by parsedate_tz() into a UTC timestamp."""
+    """Turn a 10-tuple as returned by parsedate_tz() into a POSIX timestamp."""
     if data[9] is None:
         # No zone info, so localtime is better assumption than GMT
         return time.mktime(data[:8] + (-1,))
     else:
-        t = time.mktime(data[:8] + (0,))
-        return t - data[9] - time.timezone
+        t = calendar.timegm(data)
+        return t - data[9]
 
 
 def quote(str):
diff --git a/Lib/email/test/test_email.py b/Lib/email/test/test_email.py
index 5db34dc9d77..65b3ebd2118 100644
--- a/Lib/email/test/test_email.py
+++ b/Lib/email/test/test_email.py
@@ -2585,6 +2585,12 @@ class TestMiscellaneous(TestEmailBase):
         eq(time.localtime(t)[:6], timetup[:6])
         eq(int(time.strftime('%Y', timetup[:9])), 2003)
 
+    def test_mktime_tz(self):
+        self.assertEqual(utils.mktime_tz((1970, 1, 1, 0, 0, 0,
+                                          -1, -1, -1, 0)), 0)
+        self.assertEqual(utils.mktime_tz((1970, 1, 1, 0, 0, 0,
+                                          -1, -1, -1, 1234)), -1234)
+
     def test_parsedate_y2k(self):
         """Test for parsing a date with a two-digit year.
 
diff --git a/Misc/NEWS b/Misc/NEWS
index e59ed37d611..789f7f78bb4 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -73,6 +73,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #14653: email.utils.mktime_tz() no longer relies on system
+  mktime() when timezone offest is supplied.
+
 - Fix GzipFile's handling of filenames given as bytes objects.
 
 - Issue #15101: Make pool finalizer avoid joining current thread.