diff --git a/html/ptg.html b/html/ptg.html
index d4a6855..fcea522 100644
--- a/html/ptg.html
+++ b/html/ptg.html
@@ -112,7 +112,7 @@
      <table class="table table-condensed">
       <thead><tr><th></th>
       {{#each times as |time|}}
-        <th>{{ displaytime time }}</th>
+        <th {{ activetime time }}>{{ displaytime time }}</th>
       {{/each}}
       </tr></thead>
      {{#each @root.schedule as |sched room|}}
@@ -121,7 +121,7 @@
          <span class="glyphicon glyphicon-{{sched.cap_icon}}"
                title="{{sched.cap_desc}}"></span>{{/if}}</td>
       {{#each (lookup @root.slots day) as |time|}}
-      <td>{{ roomcode @root.urls @root.schedule room time.name 0 }}</td>
+      <td {{ activetime time }}">{{ roomcode @root.urls @root.schedule room time.name 0 }}</td>
       {{/each}}
      </tr>
      {{/if}}
diff --git a/html/ptg.js b/html/ptg.js
index 237484d..cd3848b 100644
--- a/html/ptg.js
+++ b/html/ptg.js
@@ -120,6 +120,19 @@ Handlebars.registerHelper('displaytime',
   return new Handlebars.SafeString(content);
 });
 
+// Grey out cell if current time matches the slot hour
+Handlebars.registerHelper('activetime',
+                          function(time) {
+  if (time['realtime'] != undefined) {
+    var t = new Date(time['realtime']);
+    var now = new Date();
+    var diff = now.getTime() - t.getTime();
+    if (diff > 0 && diff < (1000*60*60)) {
+        return new Handlebars.SafeString('style="background-color: #eeeeee"');
+    }
+  }
+  return new Handlebars.SafeString('');
+});
 
 // What is the day today ?
 // Return Monday until Tuesday 1 UTC