What Capable Calendar is
Capable Calendar turns the dates already living on your Confluence pages into real calendars, and adds shared, saveable calendars of its own.
It comes with these features:
three page macros
Calendar
Clock
Event
a full Calendar page where saved calendars are created and managed
a page byline showing how many dates a page contains (hidden if none)
a Confluence dashboard widget to see any upcoming events you’re assigned to, and
a Capable Search panel and column for showing dates from pages (only with suite)
Events come from three sources:
Capable Event macros on pages
Confluence's own date chips on pages (paragraphs, table rows, task items, decision items), and
events saved inside a Capable calendar
Each signed-in user can also mint a personal, read-only iCal subscription link so Google, Apple or Outlook can follow a saved calendar, and a Confluence administrator can see and revoke every one of those links from a global settings tab.

#A few things worth knowing
The survey called the "By Page" colour mode unreachable. That is wrong: it is not selectable on the Calendar macro, but it IS selectable on a saved calendar's Color Scheme.
Two documented behaviours are silent failures that must survive into published docs: the macro overflow menu's Export → iCal and CSV items do nothing at all, and selecting no event types shows all of them rather than none.
#Related
The short version.
