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OneCal Reclaim.ai CalendarBridge SyncThemCalendars

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Self-Hosted Open Source Productivity AI Scheduling Calendar Synchronization

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Last Updated: 07-21-2026 04:27 AM (UTC)

Keeper

Work, personal, business, and school calendars at different providers double-book because no one system sees your real availability - Keeper solves that multi-calendar collision problem. Its pull-compare-push sync engine aggregates events from Google Calendar, Outlook/Office 365, iCloud, FastMail, any CalDAV server, or read-only iCal/ICS feeds, and pushes blocking events to one or many destination calendars so time slots align everywhere. The design is deliberately content-agnostic - it syncs timeslots, not titles or descriptions, so a personal appointment shows as busy time on your work calendar without leaking details. Sync logic is clean: events Keeper creates carry a traceable UID suffix, deletions propagate, and orphaned entries are purged automatically. A token-authenticated aggregated iCal feed combines selected calendars into one subscribable URL for Apple Calendar or Thunderbird. An optional MCP server gives AI agents read-only calendar access over OAuth 2.1 - list calendars and query events by date range, with no write capability. Built with Next.js and Bun under AGPL-3.0, the standalone Docker image bundles web, API, cron, worker, Redis, and PostgreSQL in one container, and self-hosting unlocks every Pro feature - unlimited calendars and one-minute sync intervals - for free.

Keeper

Benefits

  • One Availability, Everywhere
  • Busy blocks propagate across every linked calendar, so a booking link or colleague sees your true free time.
  • Privacy in the Design
  • Timeslot-only sync means personal event titles and details never appear on your employer's calendar.
  • Self-Hosted Pro for Free
  • Unlimited accounts, unlimited calendars, and one-minute sync intervals - features the hosted plan charges for.
  • No Orphaned Ghost Events
  • Tagged UIDs, propagated deletions, and automatic cleanup keep destination calendars accurate as sources change.

Features

  • Multi-Provider Sync
  • Google, Outlook/Office 365, iCloud, FastMail, generic CalDAV, and read-only iCal/ICS feeds.
  • Pull-Compare-Push Engine
  • Continuous aggregation with conflict reconciliation and content hashing to skip unchanged feeds.
  • Aggregated iCal Feed
  • A token-authenticated URL combining chosen calendars, subscribable from any calendar app.
  • MCP Server for AI Agents
  • Read-only calendar tools over OAuth 2.1 for Claude and other MCP clients.
  • Encrypted Credentials
  • CalDAV passwords and OAuth tokens encrypted at rest with a configurable key; SSRF protection flag.
  • One-Container Deployment
  • Standalone image bundles web, API, cron, worker, Redis, and PostgreSQL - or deploy services granularly.