Keeper

Keeper is an open-source application that synchronizes calendar events across different platforms. It allows users to pull events from remotely hosted iCal or ICS links and push them to one or more destination calendars, ensuring that time slots remain aligned across multiple accounts. This functionality is particularly useful for individuals who manage separate calendars for business, work, and personal life and need to prevent scheduling conflicts by mirroring availability across all accounts.

The software features a syncing engine that is agnostic to event content. It tracks the relationship between source and destination events to ensure that when a source event is removed, the corresponding event is deleted from the destination calendar. To maintain compatibility and tracking, events created by the tool are flagged using a specific suffix on the remote UID or assigned to a dedicated category on platforms that do not support custom UIDs.

In addition to synchronization, Keeper includes a Model Context Protocol (MCP) server. This server allows AI agents to access and interact with calendar data, extending the utility of the tool into AI-driven scheduling workflows. The application is built using Bun and TypeScript, and it relies on PostgreSQL and Redis for data storage and background job queuing.

Users can deploy the software via self-hosting using Docker and Docker Compose, which provides full access to all features and ensures data autonomy. The system is designed to be easy to install and manage, with a dedicated cron service for handling periodic synchronization tasks. It is positioned as a utility for users who require a reliable way to aggregate calendar data without manually duplicating entries across multiple services.