diff --git a/src/main/java/com/ciscospark/Client.java b/src/main/java/com/ciscospark/Client.java
index 6a15a75..7ec6f34 100644
--- a/src/main/java/com/ciscospark/Client.java
+++ b/src/main/java/com/ciscospark/Client.java
@@ -24,7 +24,7 @@
  */
 class Client {
     private static final String TRACKING_ID = "TrackingID";
-    public static final String ISO8601_FORMAT = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";
+    public static final String ISO8601_FORMAT = "yyyy-MM-dd'T'HH:mm:ss.SSSX";
 
     final URI baseUri;