timetable.js

// ==UserScript==
// @name         Tomorroland timetable line
// @namespace    http://tampermonkey.net/
// @version      1.0
// @description  Tomorroland timetable line!
// @author       fletchto99
// @match        https://timetable.aroundtheworld.tomorrowland.com/*
// @run-at       document-end
// @grant        GM_addStyle
// ==/UserScript==

GM_addStyle ( `
  .stage::before {
    content:"" !important;
    position: absolute !important;
    z-index: 1 !important;
    top: 0 !important;
    bottom: 0 !important;
    left: var(--time) !important;
    border-left: 2px dotted #ffcc5d !important;
  }
` );

(function() {
    'use strict';

    let start = 1595692800000;
    let end = 1595718000000;
    let day = 86400000;

    if (Date.now() > end) {
        end = end + day
        start = start + day
    }

    let style = () => {
        let q = Math.abs(Date.now()-start);
        let d = Math.abs(end-start);
        document.querySelectorAll(".stage").forEach(elem => {
            elem.style.setProperty('--time', Math.round((q/d)*3360) + 'px');
        })
    }

    setTimeout(style, 1)
    setInterval(style, 1000)
})();