The project will run fine when you run npm run dev and build locally.
However when you run npm run build && npm run preview you will get a 500 internal server error and the following issue will appear in the terminal:
import { GoogleCalendar, OutlookCalendar, YahooCalendar, ICalendar } from "datebook";
^^^^^^^^^^^^^^
SyntaxError: Named export 'GoogleCalendar' not found. The requested module 'datebook' is a CommonJS module, which may not support all module.exports as named exports.
CommonJS modules can always be imported via the default export, for example using:
import pkg from 'datebook';
const { GoogleCalendar, OutlookCalendar, YahooCalendar, ICalendar } = pkg;
at ModuleJob._instantiate (node:internal/modules/esm/module_job:124:21)
at async ModuleJob.run (node:internal/modules/esm/module_job:190:5)
If you copy the contents of the minified datebook.esm.min.js locally and import it it will work fine. Hope this helps troubleshoot the issues!