Make roofcam change time to be seconds from epoch

content/js/meteorogram/plot/update.js

@@ -56,9 +56,8 @@ function changeCamera() {
     // Makes image update. Image updates every (about) 2 minutes and 15 seconds.
     document.getElementById('roofCam').alt = document.getElementById('dirText').innerHTML = newDirection;
     var date = new Date();
-    // Update image every 5 minutes. The date and hours ensures that it won't use pictures
-    // from previous days/hours if the cache isn't cleared in that time frame.
-    var formatted_date = String(date.getDate()) + date.getHours() + Math.floor(date.getMinutes() / 5);
+    // Update image every 5 minutes and let the final value be in seconds since epoch.
+    var formatted_date = Math.floor(date.getTime() / 1000 / 300) * 300;
     document.getElementById('roofCam').src = METOBS_API_URL + '/pub/cache/aoss/cameras/' + newDirection +
                                              '/latest_medium.jpg?t=' + formatted_date;
 }