Get correct server time and make a moment js object for further procedures

servertime.js

import moment from 'moment';
import 'moment/locale/de';

moment().locale(window.config.app.locale);
moment.defaultFormat = window.config.app.dateFormat;

const getServerTime = async () => {
    const response = await fetch(window.location, {
        method: 'HEAD'
    });
    return response.headers.get('Date');
}

(async () => {
    let serverTime = await getServerTime();
    serverTime = new Date(serverTime).getTime();
    const offset = serverTime - Date.now();
    moment.now = function () {
        return Date.now() + offset;
    }
})();