diff --git a/app/js/clock.js b/app/js/clock.js
index 07ad2f2..cda0ba0 100644
--- a/app/js/clock.js
+++ b/app/js/clock.js
@@ -113,7 +113,7 @@
   function refresh() {
     getData();
     var now = new Date();
-    var mod = 600000 - (now.getTime() % 600000);
+    var mod = 1800000 - (now.getTime() % 1800000);
 
     refreshTimer = setTimeout(function() {refresh();}, mod + 10);