JSFiddle - React, Tailwind, and code Playground

JavaScript

"use strict";
if (new Date().getTimezoneOffset() === 0) {
    display("Can't test, local time is GMT");
} else {
    var dt1 = new Date("2015-04-15T15:30:00");
    var dt2 = new Date("2015-04-15T15:30:00Z");
    if (dt1.getTime() === dt2.getTime()) {
        display("Treated as UTC string (ES6 behavior)");
    } else {
        display("Treated as local time string (ES5 behavior)");
    }
}

function display(msg) {
    $("<p>").html(String(msg)).appendTo(document.body);
}