Geek Calendar Tool is a free Android app developed by spwebgames.com. It is a comprehensive calendar app with information on various calendar systems from around the world. The app provides information on the Mayan, Islamic, Hebrew (Jewish), French Revolutionary, Coptic, and Chinese calendars. It also includes astronomical data and a day count feature.

The app is easy to use and navigate. It comes with widgets that allow you to put the calendars on your home screen. The app is also ad-free, which makes for an uninterrupted user experience. The companion app, Geek Clock Tool, is also available for those who want to have a comprehensive timekeeping tool.