usaldav

usaldav is an open-source software project that provides a client library and command-line tools for interacting with WebDAV-based calendars and address books. It implements CalDAV and CardDAV protocols to manage calendars and contacts on servers, enabling users and applications to list, query, create, modify, and delete calendar events and address book entries.

Its data handling centers on standard formats such as iCalendar for events and vCard for contacts, with support for recurring events, time zones, and draft status. The project emphasizes interoperability, working with a wide range of CalDAV/CardDAV servers and cloud services that follow the published specifications. It also offers synchronization mechanisms to keep local data in sync with remote stores.

Architecture is modular: a core WebDAV client handles authentication and HTTP operations, while separate CalDAV and CardDAV modules implement server-specific operations. Optional storage backends and caches enable offline work and fast access. The library provides a stable API for developers and a command-line interface for end users, with TLS and common authentication methods.

Usage and ecosystem: typical deployments include personal automation scripts, data migration, and integration with personal information managers. It is designed to be extensible via plugins or adapters for different servers and environments. As an open-source project, it is maintained by a community of contributors and documented with API references and quick-start guides.