diff --git a/Lib/http/cookiejar.py b/Lib/http/cookiejar.py
index 7f7f55b..cb553db 100644
--- a/Lib/http/cookiejar.py
+++ b/Lib/http/cookiejar.py
@@ -31,6 +31,7 @@ __all__ = ['Cookie', 'CookieJar', 'CookiePolicy', 'DefaultCookiePolicy',
 import copy
 import re
 import time
+import datetime
 import urllib.parse, urllib.request
 try:
     import threading as _threading
@@ -97,10 +98,11 @@ def time2isoz(t=None):
     1994-11-24 08:49:37Z
 
     """
-    if t is None: t = time.time()
-    year, mon, mday, hour, min, sec = time.gmtime(t)[:6]
-    return "%04d-%02d-%02d %02d:%02d:%02dZ" % (
-        year, mon, mday, hour, min, sec)
+    if t is None:
+        dt = datetime.datetime.utcnow()
+    else:
+        dt = datetime.datetime.utcfromtimestamp(t)
+    return dt.strftime("%Y-%m-%d %H:%M:%SZ")
 
 def time2netscape(t=None):
     """Return a string representing time in seconds since epoch, t.