Note: After saving, you have to bypass your browser's cache to see the changes. Google Chrome, Firefox, Microsoft Edge and Safari: Hold down the ⇧ Shift key and click the Reload toolbar button. For details and instructions about other browsers, see Wikipedia:Bypass your cache.
'use strict';
// See [[phab:T389161]]
mw.loader.using('mediawiki.DateFormatter', require => {
    const DateFormatter = require('mediawiki.DateFormatter');
    const date = new Date();
    console.log(DateFormatter.formatTimeAndDate(date));
    console.log(DateFormatter.forUtc().formatTimeAndDate(date));
});