Cal.rs

Cal.rs is a scheduling platform designed for users who want to host their own infrastructure without relying on external services or subscriptions. It runs as a single Rust binary, requiring no Node.js, PostgreSQL, or SaaS fees. The platform connects to CalDAV, Google Calendar, and Microsoft Exchange to sync availability, then lets users define bookable meeting types and share booking links with guests.

Key features include timezone-aware scheduling with automatic guest timezone detection, email and SMS notifications with calendar invites, pending booking approval workflows, and the ability for guests to reschedule meetings. The availability engine computes free/busy slots from calendar events, availability rules, existing bookings, and buffer times. According to the source, Cal.rs was built using Claude Code.