Firestore Timestamp.fromDate not UTC

Anyone knows how to persist UTC Timestamp in Firestore?

In my Angular app, if I convert today's date to a Timestamp like the following and I end up with a UTC+2 (it's summer time here right now in Switzerland) date in the Firestore database

import {firebase} from '@firebase/app';
import '@firebase/firestore';

const myTimestamp = firebase.firestore.Timestamp.fromDate(new Date());

If for example I try to convert a date from the winter time, I end up with UTC+1 Timestamp in the database

const myTimestamp = firebase.firestore.Timestamp.fromDate(new Date(2019, 0, 1));

If I would use now() I end up with UTC+2 dates too

const now: firebase.firestore.Timestamp = firebase.firestore.Timestamp.now();

I don't do anything particular when I persist the data:

const now: firebase.firestore.Timestamp = firebase.firestore.Timestamp.now();
const myTimestamp = firebase.firestore.Timestamp.fromDate(new Date());

const myData = {
    created_at: now,
    another_value: myTimestamp
};

await this.collection.add(myData);

Any idea how is it possible to create valid UTC Timestamp for Firestore?

Firestore timestamps don't have a timezone encoded into them. It just stores the offset from the Unix epoch using a combination of seconds and nanoseconds (which are fields on the Timestamp object). Most date/time objects are like this - they don't care what the timezome is, it's just an absolute point in time.

If you view a timestamp field in the console, you will see the time displayed in the local timezone that your computer uses from its local settings.

If you convert a timestamp to a JavaScript Date object, that date object naturally renders itself in the browser's local timezome, similar to the console.

If you want to render a Date object for a specific timezone, you should use a library to do that for you, such as moment.js.