JS-decoder generate timestamp with local timezone

I am currently trying to log LoRa-data onto a Beckhoff PLC.
So far I installed the RaspberryPi1 Chirpstack OS image on a Raspberry Pi 2 and set up three sensor knots of which one is an Arduino.
Thanks to the work of Brocaar, everything was set up easy, fast (approx. half a day, the second time), and is now running happily.

The only problem I have:
My Sensors do not have an RTC module included, therefore I want to use the Raspberry Pi system time as a timestamp with local time in the decoder.

So far I tried the following to change the time:
var timestamp=new Date().toLocaleString('de-DE',{timezone:'Europe/Zurich'});
var utctime=new Date();
var timestamp=utctime.toLocaleString('de-DE',{timezone:'Europe/Zurich'});
Both didn’t work, the time format stays in UTC and YY-MM-DD HH:MM:SS.
And even this does not work as expected:
var CEST=2;
var CET=1;
var utctime= new Date();
var localtime=utctime.setHours(utctime.getHours()+CEST);
var timestamp=localtime.toLocaleString();

Also trying to change the system time didn’t work because of the lack of tools in the OS.
Hence the second setup: I screwed up so badly, the application server refused to work.

Therefore I would like to ask if there is an easy way to get this to work.

Thanks in advance