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An API that generates the Roman Catholic liturgical calendar for any given year, based on the General Roman Calendar. It calculates mobile festivities, handles precedence rules, and supports national and diocesan calendars. Calendar data is served in JSON, YAML, XML, or ICS format.

For Users

Subscribe to the liturgical calendar in your calendar app.

• Calendar subscriptions — Subscribe in Google Calendar, iPhone, Outlook, and more
• Alexa skill — Liturgy of the Day newsbrief for Amazon Alexa

For Webmasters

Display liturgical calendar data on your website using the official component libraries.

• Using the API on your website — Component libraries for PHP and JavaScript

For Liturgists

Contribute your liturgical expertise by editing calendar definitions or creating correctness tests.

• Editing calendars and tests — How to become a calendar editor or test editor

For Developers

Integrate the Liturgical Calendar API into your applications.

• API Reference — Routes, request parameters, and response structure
• API keys — Register as a developer, create an application, and generate API keys
• Examples — Standalone code examples for PHP, JavaScript, and FullCalendar
• OpenAPI documentation — Interactive Swagger docs

For Contributors

Help develop the Liturgical Calendar project.

• Getting started — Environment setup, running the server, and running tests
• Source data — How the liturgical calendar source data is organized
• Translating — Contributing translations via Weblate

Testing

• How to write unit tests — PHPUnit test infrastructure
• Liturgical event tests — JSON-based liturgical correctness tests
• Unit Test server and interface — WebSocket test server and frontend

Authentication & RBAC

• Zitadel RBAC Overview — Architecture, roles, protected routes, and key components
• Calendar Governance Model — The ecclesial governance model: Holy See, Conferences of Bishops, dioceses
• OpenFGA Fine-Grained Authorization — Relationship-based per-calendar permissions with OpenFGA
• Zitadel Infrastructure Setup — Local development setup with Docker Compose
• Zitadel Production Deployment — Step-by-step production deployment guide
• Zitadel Production Security — Security configuration, rate limiting, HTTPS, cookies
• Zitadel Implementation Status — What's complete and what's still outstanding