Publish a live calendar feed from Google Sheets to Google, Apple and Outlook

Description

Quick Overview
This workflow serves a token-protected iCalendar (.ics) feed from a Google Sheets “events” tab, so Google Calendar, Apple Calendar, and Outlook can subscribe to a live calendar URL.

How it works
Receives an incoming webhook request for calendar.ics and checks the ?token= query parameter against the configured feed token.
Looks up a short-lived cached .ics response and immediately serves it when it is still fresh.
If the cache is stale, reads event rows from a Google Sheets document and continues even if the sheet read errors.
Validates and normalizes each row (including all-day vs timed events, status values, and a past/future time window) and drops malformed or out-of-window entries.
Renders the remaining events into an RFC 5545 iCalendar text body (with correct escaping, CRLF line endings, and UTC timestamps) and optionally adds a “feed health” event.
Stores the generated .ics in workflow static data for caching and responds with text/calendar, serving the last known good calendar when a sheet read/render failure occurs or returning 404/503 on unauthorized/unavailable requests.

Setup
Add Google Sheets OAuth credentials, select the target spreadsheet in the Google Sheets read step, and create a tab named events with the required headers (uid, title, start_date, start_time, end_date, end_time, location, description, status, updated_at, rrule).
In the feed configuration, replace feed_token with a long random secret, set a unique feed_namespace, and review timezone/window/default duration settings to match your spreadsheet and desired publish range.
Activate the workflow, copy the production webhook URL for calendar.ics, append ?token=YOUR_TOKEN, and use that URL to subscribe from Google Calendar, Apple Calendar, or Outlook.