hswaw/checkinator: convert timestamp to browsers timezone

Change-Id: Ib7439269bf13de530a5f170bf231f89d815b0f3e
Reviewed-on: https://gerrit.hackerspace.pl/c/hscloud/+/1246
Reviewed-by: q3k <q3k@hackerspace.pl>
diff --git a/hswaw/checkinator/at/templates/main.html b/hswaw/checkinator/at/templates/main.html
index 6012b21..36ab1cd 100644
--- a/hswaw/checkinator/at/templates/main.html
+++ b/hswaw/checkinator/at/templates/main.html
@@ -9,7 +9,7 @@
   {% for user, timestamp in users %}
     <li>
       <a href="{{ user | wikiurl }}">
-      {{ user }} ({{ timestamp|strfts() }})
+          {{ user }} (<span class="timestamp" data-datetime="{{ timestamp|utcisoformat }}">{{ timestamp|strfts() }} UTC</span>)
       </a>
     </li>
   {% endfor %}
@@ -31,4 +31,19 @@
   {% endtrans %}
   <hr>
   <a href="claim">Claim this device!</a>
+  <script>
+    function formatDate(d) {
+      function pad(n) {return n<10 ? '0'+n : n};
+      return d.getFullYear()+'-'
+       + pad(d.getMonth()+1)+'-'
+       + pad(d.getDate())+' '
+       + pad(d.getHours())+':'
+       + pad(d.getMinutes());
+    }
+
+    for (const tstamp of document.getElementsByClassName('timestamp')) {
+      const dt = new Date(tstamp.getAttribute("data-datetime"));
+      tstamp.innerHTML = formatDate(dt);
+    }
+  </script>
 {% endblock %}