diff --git a/lib/savon/core_ext/time.rb b/lib/savon/core_ext/time.rb
index 36d6674b..55aa99d9 100644
--- a/lib/savon/core_ext/time.rb
+++ b/lib/savon/core_ext/time.rb
@@ -4,7 +4,15 @@ module Time
 
       # Returns an xs:dateTime formatted String.
       def xs_datetime
-        strftime "%Y-%m-%dT%H:%M:%S%Z"
+        zone = if utc_offset < 0
+          "-#{"%02d" % (- utc_offset / 3600)}:#{"%02d" % ((- utc_offset % 3600) / 60)}"
+        elsif utc_offset > 0
+          "+#{"%02d" % (utc_offset / 3600)}:#{"%02d" % ((utc_offset % 3600) / 60)}"
+        else
+          "Z"
+        end
+
+        strftime "%Y-%m-%dT%H:%M:%S#{zone}"
       end
 
     end
diff --git a/spec/savon/core_ext/time_spec.rb b/spec/savon/core_ext/time_spec.rb
index 92676617..9e8ebcda 100644
--- a/spec/savon/core_ext/time_spec.rb
+++ b/spec/savon/core_ext/time_spec.rb
@@ -6,7 +6,7 @@
     let(:time) { Time.utc(2011, 01, 04, 13, 45, 55) }
 
     it "should return an xs:dateTime formatted String" do
-      time.xs_datetime.should == "2011-01-04T13:45:55UTC"
+      time.xs_datetime.should == "2011-01-04T13:45:55Z"
     end
   end