What's the purpose of Calendar Event Groups?

I use calendars for call routing but have never used calendar event groups. I took a look a the wiki but it doesn’t really explain what the purpose of the calendar event groups is.

What’s the use case for it? what does it do?

Per the wiki:Calendar Event Groups Module - PBX GUI - Documentation
Calendar event groups are a collection of calendars, events or categories from the Calendar Module.

Multiple calendars, events and/or categories can be placed into separate groups. Even multiple events from different calendars can be placed into a single group!

These groups can then be linked to various applications or utilities…

To me this reads as a way to consolidate calendars (Holiday Calendar, Hours of Operation Calendar, Receptionist Calendar) that are used for different purposes outside of the PBX, but are able to have a consolidated view for the PBX routing via the calendar function.

ok yeah, that still doesn’t give me a clue about how they work in practice…

https://wiki.freepbx.org/display/FPG/Calendar+Module#CalendarModule-ModuleSupport

Says in the linked documentation, there are even pictures.

" Calendar Group: The calendar group to use. For every matching event the time condition will be matched"

Supported modules: