public static void scheduleSynchronization(Context ctx, long delta, boolean cancel) {
    SharedPreferences pref = PreferenceManager.getDefaultSharedPreferences(ctx);
    long interval = Integer.parseInt(pref.getString(SYNC_INTERVAL, DEFAULT_SYNC_INTERVAL)) * 1000L;

    Intent intent = new Intent(ctx, AlarmReceiver.class);
    PendingIntent sender = PendingIntent.getBroadcast(ctx, 0, intent, PendingIntent.FLAG_CANCEL_CURRENT);
    AlarmManager am = (AlarmManager) ctx.getSystemService(Context.ALARM_SERVICE);
    am.cancel(sender);

    boolean canUseNetwork = getNetworkState(ctx) == CAN_USE_NETWORK;

    if (!cancel && canUseNetwork && pref.getBoolean(AUTO_SYNC, false)) {
      int mode = pref.getBoolean(WAKE_ONLY, false) ? ELAPSED_REALTIME : ELAPSED_REALTIME_WAKEUP;

      final long elapsed = SystemClock.elapsedRealtime();
      final long firstFireTime = delta == 0 ? elapsed + interval : elapsed + delta;

      if (pref.getBoolean(EditPreferences.STRICT_INTERVAL, false)) {
        am.setRepeating(mode, firstFireTime, interval, sender);
      } else {
        am.setInexactRepeating(mode, firstFireTime, interval, sender);
      }
      Log.d(ClockSync.TAG, "Timer set, interval: " + interval / 1000);
    } else {
      Log.d(ClockSync.TAG, "Timer cancelled");
    }
  }