Best Open Source Calendar Software 2026

Calendar Software

Calendar Calculators Clear Filters

Browse free open source Calendar software and projects below. Use the toggles on the left to filter open source Calendar software by OS, license, language, programming language, and project status.

$300 Free Credits to Build on Google Cloud
New customers can spin up VMs, build with AI, and query data at no cost.

Put your $300 in credit toward real workloads, then keep building with free monthly usage for 20+ products. No commitment and no charge until you upgrade.

Start Free
Ship Agents Faster
Transform your applications and workflows into powerful agentic systems at global scale.

Gemini Enterprise Agent Platform lets you rapidly build, scale, govern and optimize production-ready agents grounded in your organization's data. The platform enables developers to build custom or pre-built agents for virtually any use case. New customers get $300 in free credits.

Start Free
1

Osmo

Osmo is a handy personal organizer, which includes calendar, tasks manager, address book and notes modules. It was designed to be a small, easy to use and good looking PIM tool to help to manage personal information.

23 Reviews

Downloads: 15 This Week

Last Update: 2024-11-20
See Project
2

DateCalc

A calculator for dates. May calculate how many days there are between two dates or the next date from a starting date. Runs on Palm Os and Windows.

Downloads: 0 This Week

Last Update: 2015-09-01
See Project
3

DiesAdQuem Calculator

Calculate the Dies ad quem day

El programa cuenta plazos es un programa que ayuda a los abogados a calcular el día Dies ad quem. Help to the barriesters, lawyers and solicitors to calculate the Dies ad quem. En el mundo legal, dependiendo del tipo de proceso, hay unos plazos para presentar, alegar, etc. Pero en estos plazos, dependiendo también del tipo de proceso, se debe de contar o no los Sábados, y en algunos, tener en cuenta los festivos nacionales, festivos autonómicos y locales.

Downloads: 0 This Week

Last Update: 2014-08-26
See Project
4

ObjectLab Kit

We MOVED to GITHUB!

http://github.com/Appendium/objectlabkit A set of modules to handle common financial functions. The first module is Date Calculator which handles holidays and weekends. A set of rules are implemented to deal with days falling on a holiday: Forward, Backward, Modified Forward, Modified Backward New FX Rate Calculators

Downloads: 0 This Week

Last Update: 2014-10-09
See Project
Custom VMs From 1 to 96 vCPUs With 99.95% Uptime
General-purpose, compute-optimized, or GPU/TPU-accelerated. Built to your exact specs.

Live migration and automatic failover keep workloads online through maintenance. One free e2-micro VM every month.

Start Free