Writing and programming of calendars

Link to https://myros-code.github.io/Calendars/
Writing and programming of two calendars.
The calendar has a simple functional (the customer does not need to be more), written on a clean JavaScript.

What is the convenience of such calendars if there are a lot of plugins? - As the customer doesn't need a lot of such a calendar, it's no sense to load the site with extra plugins.
Link to https://myros-code.github.io/Calendars/