diff --git a/activesupport/test/message_encryptor_test.rb b/activesupport/test/message_encryptor_test.rb
index bd11b76e60a973159ad8c01d3c5d52bbe252bc4d..95e64fe6d11f4a2f3df88b19734eb726d0f7f56a 100644
--- a/activesupport/test/message_encryptor_test.rb
+++ b/activesupport/test/message_encryptor_test.rb
@@ -44,8 +44,8 @@ def test_alternative_serialization_method
     @encryptor.serializer = lambda { |value| ActiveSupport::JSON.encode(value) }
     @encryptor.deserializer = lambda { |value| ActiveSupport::JSON.decode(value) }
     
-    message = @encryptor.encrypt_and_sign({ :foo => 123, 'bar' => Time.local(2010) })
-    assert_equal @encryptor.decrypt_and_verify(message), { "foo" => 123, "bar" => "2010-01-01T00:00:00-05:00" }
+    message = @encryptor.encrypt_and_sign({ :foo => 123, 'bar' => Time.utc(2010) })
+    assert_equal @encryptor.decrypt_and_verify(message), { "foo" => 123, "bar" => "2010-01-01T00:00:00Z" }
   end
 
   private
diff --git a/activesupport/test/message_verifier_test.rb b/activesupport/test/message_verifier_test.rb
index 83f34ebc339d495331921aeaa255b981c4a61393..224e38a52a6159b8b222062453d4b8511f234275 100644
--- a/activesupport/test/message_verifier_test.rb
+++ b/activesupport/test/message_verifier_test.rb
@@ -37,8 +37,8 @@ def test_alternative_serialization_method
     @verifier.serializer = lambda { |value| ActiveSupport::JSON.encode(value) }
     @verifier.deserializer = lambda { |value| ActiveSupport::JSON.decode(value) }
     
-    message = @verifier.generate({ :foo => 123, 'bar' => Time.local(2010) })
-    assert_equal @verifier.verify(message), { "foo" => 123, "bar" => "2010-01-01T00:00:00-05:00" }
+    message = @verifier.generate({ :foo => 123, 'bar' => Time.utc(2010) })
+    assert_equal @verifier.verify(message), { "foo" => 123, "bar" => "2010-01-01T00:00:00Z" }
   end
 
   def assert_not_verified(message)