Adjusting for timezone to display the time on an analogue clock

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1

Edit - "function node" and "template node" swapped over.

If I use a function node I can adjust the UTC timestamp from new Date() to account for BST

let d = new Date();                           // eg 2021-10-02T14:11:35.000Z
let ts = d.getTime();                         // current timestamp in UTC
let offset = (d.getTimezoneOffset() * 60000); // BST getTimezoneOffset returns -60 minutes
let adjustedts = (ts - offset);               // Adjust the timestamp
let adjusteddate = new Date(adjustedts);      // eg 2021-10-02T15:11:35.000Z
msg.payload = adjusteddate;
return msg;

But when I transfer that code to a script in a template node it doesn't work, the offset always seems to be 0

<script>
(function(scope) {
  scope.$watch('msg', function(msg) {
    if (msg) {
        let d = new Date();                           // eg 2021-10-02T14:11:35.000Z
        console.log("UTC hour ", d.getHours());
        let ts = d.getTime();                         // current timestamp in UTC
        let offset = (d.getTimezoneOffset() * 60000); // BST getTimezoneOffset returns -60 minutes
        console.log("offset", offset);
        let adjustedts = (ts - offset);               // Adjust the timestamp
        let adjusteddate = new Date(adjustedts);      // eg 2021-10-02T15:11:35.000Z

        let sec = adjusteddate.getSeconds();
        let mins = adjusteddate.getMinutes();
        let hour = adjusteddate.getHours();
        console.log("hour ", hour);
        
        let secDeg = ''+(((sec / 60) * 360) + 90)+'deg'; 
        let minsDeg = ''+(((mins / 60) * 360) + ((sec/60)*6) + 90)+'deg';         
        let hourDeg = ''+(((hour / 12) * 360) + ((mins/60)*30) + 90)+'deg';
        
        document.getElementById('gauge_'+scope.$id).style.setProperty('--time-hour', hourDeg);
        document.getElementById('gauge_'+scope.$id).style.setProperty('--time-minute', minsDeg);
        document.getElementById('gauge_'+scope.$id).style.setProperty('--time-second', secDeg);
    }
   
  });
})(scope);
</script>

The three console.log() statements give
Untitled 1

I'm guessing this is something to do with scope (which I don't understand in javascript)?
Can anyone point me in the right direction?

2

Is node-red and the client browser on the same machine and do they have the same timezone setting?

3

Node-red is on a Raspberry Pi - date shows Sat 2 Oct 16:16:06 BST 2021
The browser is on WIndows 10 and the time shows as 16:16:20 Sat 2 October 2021 (it automatically adjusts the clock GMT/BST)

Ah. The function code runs on the Pi, the template on the PC, presumably.
Does getTimezoneOffset() work in a browser on a PC?

4

Yes.

On PI, What does cat /etc/timezone show?

On windows, what timezone is set?

5

pi $ cat /etc/timezone
Europe/London

PC
Untitled 2

6

Hmm my browser clearly doesn't think summer time applies here.
My PC knows it's 20:15 but my browser says d.getHours() and d.getUTCHours() are both 19.

Nailed it!
about:config privacy.resistFingerprinting was set to true.
Set it back to default, restarted Firefox (cleared the cache) and it's working now.