diff --git a/dummyserver/handlers.py b/dummyserver/handlers.py
index 0a37fc5500..1c8e9b6c86 100644
--- a/dummyserver/handlers.py
+++ b/dummyserver/handlers.py
@@ -321,7 +321,7 @@ def redirect_after(self, request):
         date = request.params.get("date")
         if date:
             retry_after = str(
-                httputil.format_timestamp(datetime.fromtimestamp(float(date)))
+                httputil.format_timestamp(datetime.utcfromtimestamp(float(date)))
             )
         else:
             retry_after = "1"