diff --git a/packages/lit-dev-content/samples/examples/properties-custom-converter/index.html b/packages/lit-dev-content/samples/examples/properties-custom-converter/index.html
index 11cb69ae8..75d23e9ec 100644
--- a/packages/lit-dev-content/samples/examples/properties-custom-converter/index.html
+++ b/packages/lit-dev-content/samples/examples/properties-custom-converter/index.html
@@ -11,6 +11,6 @@
 <body>
   <my-element></my-element>
   <hr>
-  <my-element date="Oct 20 2021Z-08:00"></my-element>
+  <my-element date="Oct 20 2021"></my-element>
 </body>
 </html>
