Consider using an calendar js library

Problem/Motivation

As new features are added, the js might quickly become harder to maintain.
There are also accessibility and localization concerns that might be missing.

Proposed resolution

There are several js projects available for the calendar part. Haven't found any that made both the calendar and slots.
This was the closest I've found:
https://github.com/flatpickr/flatpickr
Unfortunately, it seems no longer maintained :(

If you know an open-source project that could be a good fit, please add it here.
A few features that should support:

• Allow to select a start and end date
• Allow to add unavailable days and periods
• Hooks for month change and select (we'll need it for the slots)
• Accessibility an i11n support