Now the United Nations offers a free app for its Calendar of Observances.
This free iOS app features official United Nations observances and links to related videos and further information. It also illustrates how the UN makes a difference in tackling global challenges. The UN Calendar can store UN observances in the native calendar, or it can be used independently. The app functions in Chinese, Spanish and English. Arabic, French and Russian will be available in early 2014.
Be ready for World Day of Social Justice on February 20!
If you don't want to use the app, you can always visit this list of United Nations observances.
And it you do like iOS apps, you don't have to stop with the calendar. In the App Store you'll also find UN CountryStats ("a data visualization tool to compare key economic, social, environmental, trade, and area & population indicators for 216 countries and territories") and the UN News Reader ("for quick and easy access to all stories from the UN News Centre"). More UN apps are listed here.
Graphic from UN calendar app page.