An open-source calendar with a web app and a REST API, so an AI assistant can check availability, spot conflicts and book events in a local calendar, with adapters for Google, Outlook and CalDAV.
AI assistants can talk about a schedule but can't safely act on it. Every calendar service has its own API, and nothing stops an assistant from double-booking someone.
One npm workspace: a React 19 web app (month, week, day and agenda views, drag to reschedule) and a Node and Express 5 API with endpoints for availability, conflicts, booking and editing. Providers share one contract: a local file by default, plus Google, Outlook and CalDAV adapters. Repeating events, working hours, time zones, reminders, search and ICS import and export are all built in, and a written guide tells assistants how to use the API.
177 automated tests across 15 suites, about 96% line coverage, run by GitHub Actions on every push to master and every pull request. Code-review findings were written as failing tests first, then fixed. The Google, Outlook and CalDAV adapters are tested against stand-ins; the local provider is the one running for real.