From 6577bb44354778eaa19fffa4b5f60811c72e76db Mon Sep 17 00:00:00 2001
From: Christian Pointner <equinox@helsinki.at>
Date: Sun, 19 Jul 2015 14:55:41 +0200
Subject: remove week from rd-ntp protocol and readed javascript based
 calculation


diff --git a/www/js/utils.js b/www/js/utils.js
index b8bbd76..eec81b0 100644
--- a/www/js/utils.js
+++ b/www/js/utils.js
@@ -74,10 +74,32 @@ function msToTimeString(time) {
   return h + ':' + m.pad(2) + ':' + s.pad(2) + '.' + hs;
 }
 
+function get_rd_week(msEpoch) {
+  //
+  // This computes the current Rivendell Week based on the number
+  // of weeks since epoch.
+  //
+  // Explanation:
+  //  epoch was at 01.01.1970 which was a Thursday.
+  //  Monday in that week is (s-from-epoch + 3*24*60*60) seconds ago.
+  //  This needs to be adjusted by the timezone offset for Europe/Vienna
+  //  which is of course not constant (damn you daylight savings time)
+  //  Divide this by (7*24*60*60) and you get the number of
+  //  weeks since the Monday in the week of epoch adjusted for timezone offsets.
+  //  This week had week number 3 so add an offset of 2 and
+  //  get the modulo of 4. This rounded down gives you the current week
+  //  with 0 meaning Week 1. So add 1 to that number and you will get
+  //  the current RD week.
+  //
+  var sEpoch = ((+msEpoch) / 1000) ;
+  var week = Math.floor((((sEpoch + 259200)/604800) + 2) % 4) + 1;
+  return week;
+}
+
 function Clock(draw_callback) {
   this.draw_callback = draw_callback;
 
-  this.last_message = { t1: 0, t2: 0, t3: 0, t4: 0, tz_offset: 3600, week: 3 };
+  this.last_message = { t1: 0, t2: 0, t3: 0, t4: 0, tz_offset: 3600 };
   this.clock_offset = 0;
   this.clock_rtt = 0;
 
@@ -92,7 +114,7 @@ function Clock(draw_callback) {
     time_str += (rdtime.getUTCMinutes() > 9 ? ':' : ':0') + rdtime.getUTCMinutes();
     time_str += (rdtime.getUTCSeconds() > 9 ? ':' : ':0') + rdtime.getUTCSeconds();
 
-    this.draw_callback(date_str, time_str, this.last_message.week);
+    this.draw_callback(date_str, time_str, get_rd_week(rdtime_ms));
   }
 
   this.ntp_update = function(event) {
-- 
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