Free Alarm Clock - Free Alarm Clock is a free, full-featured and user-friendly computer alarm clock for Windows.
Gnome Clocks - Clock application designed for GNOME 3
Digital Clock 4 - Beautiful customizable clock with plugins
Simple Calendar - A simple calendar with events (optional recurring and reminders), week numbers and a customizable...
Just a clock - This is an opensource app for Android
Simple Alarm Clock - Simple open source alarm application for Android devices.