Calendar GitHub Repositories (2026) · Open Source Tools

MailCraft: an open-source, clean-room mail, calendar and contacts program in pure Rust, for Microsoft 365, Outlook.com and IMAP. Early alpha.

A native, open-source macOS all-in-one productivity app built in Swift, designed for deep focus and visual clarity.

Full-sized drag & drop event calendar in JavaScript

Leantime is a goals focused project management system for non-project managers. Building with ADHD, Autism, and dyslexia in mind.

Mail and calendar for Linux and macOS. Gmail and IMAP accounts, Google Calendar, contacts, OpenPGP and S/MIME. GTK4 and libadwaita, written in Rust.

Android open source calendar

Built from the ground up for speed. Flectar Mail delivers native performance, instant startup, and about 20 MB of private memory at idle.

One home instead of many subscriptions. Yuvomi is a self-hosted family planner: tasks, calendar, budget, meals, shopping, health and more in one PWA on your own server or NAS. Docker, Podman, TrueNAS, Umbrel, Unraid, Portainer, Home Assistant, YunoHost, Proxmox. No tracking, MIT.

Sync your Outlook and Google calendars

A compact lunar calendar for your macOS menu bar.

A beautiful, custom Home Assistant calendar card

A completely free ITSM tool

🇺🇦 Your meetings at your fingertips in the macOS menu bar

Clendar - Minimal Calendar app. Written in SwiftUI.

Atom Agent, Open-Source Governed AI Agent Platform for Self-Hosted Automation

EspoCRM – Open Source CRM Application

Terminal-first calendar, todo, and journal manager with iCalendar (RFC 5545) support and CalDAV sync — CLI + TUI, local SQLite storage

Easily access public holidays for 200+ countries via .NET, REST API, Docker, or NuGet for online and offline use.

:blue_book: A diary application optimized for user experience.

📅 Calendar link generator for popular services