Umstellung auf UTC Timestamp

lib/content_views/approach_area_page.dart

@@ -195,7 +195,7 @@ class _ApproachAreaPageState extends State<ApproachAreaPage> with ProducerMixin,
 
     if (position != null) {
       setPosMessage.track = ZipTrack();
-      setPosMessage.track!.time = DateTime.now().toIso8601String();
+      setPosMessage.track!.time = Util.toUnixMillisUtc(DateTime.now());
       setPosMessage.track!.pos = ZipTrackPos();
       setPosMessage.track!.pos!.lat = position.latitude;
       setPosMessage.track!.pos!.long = position.longitude;