Tampermonkey script to view "office" time

slack_second_time.js

// ==UserScript==
// @name         Second timezone for Slack web client
// @namespace    http://vanadium23.me/
// @version      0.1
// @description  Add second time on element hover
// @author       vanadium23
// @match        https://app.slack.com/client/*
// @icon         data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==
// @grant        none
// ==/UserScript==

(function() {
    'use strict';
    // set your targetTimezone different from local
    const targetTimezone = 'Europe/Belgrade';


    document.body.addEventListener('mouseover', (event) => {
        if (event.target.classList.contains('c-timestamp__label')) {
            let localTime = event.target.innerText;
            if (localTime.indexOf('/') !== -1) {
                // already converted
                return;
            }
            const parentNode = event.target.parentNode;
            const timestamp = parseInt(parentNode.dataset.ts)*1000;
            const localDateTime = new Date(timestamp);
            const targetTime = new Intl.DateTimeFormat('en-US', {
                timeZone: targetTimezone,
                hour: '2-digit',
                minute: '2-digit',
                hour12: false,
                timeZoneName: "shortGeneric",
            }).format(localDateTime);

            event.target.innerText = `${localTime} / ${targetTime}`;
        }
    });
})();