icalnet

IcalNet is an open-source platform for aggregating, indexing, and querying iCalendar data from multiple sources into a unified calendar view. It provides a RESTful API and a pluggable ingestion pipeline designed to support interoperability between calendar services that expose iCalendar data.

The project aims to improve data compatibility among calendar tools by offering a common internal event model, support for standard ICS formats, and scalable querying capabilities. Its architecture is modular, consisting of an ICS parser, a normalizer that maps ICS components to a unified event representation, a storage layer, and an API layer that serves event and calendar metadata.

The core data model represents events with fields such as id, start, end, duration, recurrence rule (RRULE), summary, description, location, time zones, attendees, and reminders. It fully supports iCalendar recurrence rules and timezone-aware scheduling, and it includes basic de-duplication and conflict-resolution mechanisms when merging multiple sources.

IcalNet can ingest calendars via ICS files, CalDAV endpoints, or direct URL feeds, and exposes endpoints for event search, calendar listing, and metadata filtering by time range, attendee, or location. The project emphasizes privacy-aware access control and commonly uses API keys or OAuth 2.0 for authentication.

Released as open-source software, it is maintained by a community of contributors with documentation describing installation, integration, and security considerations. Related standards include iCalendar, ICS, and CalDAV.