Is it possible with vanilla JS to display foreign user time with his timezone?

Example:

• ME: I am located in Prague (GMT+1)
• USER: Is located in New York (EDT)

Current time is const localTime = 20:53 GMT+1

Current USER time is const userTime = 15:53 EDT - this is what I want to display to me: USER's time is 15:53 EDT

When USER is logged in in the beginning. I store his timezone offset: const tzOffset = new Date().getTimezoneOffset() Which returns difference from UTC in minutes.

How to with vanilla js display userTime 15:53 EDT using this tzOffset?

I have tried DateTimeFormat but options.timezone does not accept that tzOffset. And new Date has just toLocaleString().

Is there any easy way?

Edit:

Maybe better example

I have chat and there is me and the USER. If I hover over the USER I want to display a tooltip with his time with his timezone. Only what I have on my client is Date.prototype.getTimezoneOffset().

it is easy to add Hours to my current new Date() and get his time. But it is hard to display his timezone - EDT, GMT+/-X etc..