No calendars linked yet.
iCloud: Open Calendar on Mac or icloud.com → right-click a calendar → Share Calendar → toggle Public Calendar → copy the URL → paste it above.
Google: Calendar settings → pick a calendar → scroll to Integrate Calendar → copy Secret address in iCal format.
Anyone with the URL can read the calendar's events, so don't share it publicly. The URL is stored on the server in your private Cloudflare KV.