diff --git a/app/assets/javascripts/cookieMessage.js b/app/assets/javascripts/cookieMessage.js
index e6419bd35..ffd906d34 100644
--- a/app/assets/javascripts/cookieMessage.js
+++ b/app/assets/javascripts/cookieMessage.js
@@ -9,14 +9,14 @@ window.GOVUK.Modules = window.GOVUK.Modules || {};
 
     // clear old cookie set by our previous JS, set on the www domain
     if (window.GOVUK.cookie('seen_cookie_message')) {
-      document.cookie = 'seen_cookie_message=;expires=' + new Date() + ';path=/';
+      document.cookie = 'seen_cookie_message=;expires=' + new Date().toGMTString() + ';path=/';
     }
 
     if (consent === null) {
       for (var i = 0; i < gaCookies.length; i++) {
         if (window.GOVUK.cookie(gaCookies[i])) {
           // GA cookies are set on the base domain so need the www stripping
-          var cookieString = gaCookies[i] + '=;expires=' + new Date() + ';domain=' + window.location.hostname.replace(/^www\./, '.') + ';path=/';
+          var cookieString = gaCookies[i] + '=;expires=' + new Date().toGMTString() + ';domain=' + window.location.hostname.replace(/^www\./, '.') + ';path=/';
           document.cookie = cookieString;
         }
       }