Open Source Alternatives to OneCal

A calendar synchronization tool that syncs Outlook, iCloud, and Google Calendars in real time to prevent double booking. The software provides a unified calendar interface for managing multiple accounts and allows users to share scheduling links to coordinate meetings. It is designed for individuals and teams who need to coordinate work and personal schedules across different providers without manual entry. The product is deployed as a cloud service that supports unlimited sync configurations between connected calendars. Users can invite team members to a plan and are charged per additional user based on the selected tier. The service includes a data processing addendum for security and compliance. The product is available through various subscription tiers based on the total number of connected calendars required by the user.

Whether you want to cut software costs or escape vendor lock-in, these open source alternatives to OneCal give you an option you fully own. You can self-host them, so your data stays on infrastructure you control. This page lists 1 open source alternative to OneCal. The most popular is Keeper. It uses the AGPL-3.0 license and ships an official Docker image.