United Nations Observances

The United Nations observes designated days, weeks, years, and decades, each with a theme, or topic. By creating special observances, the United Nations promotes international awareness and action on these issues.  The majority of observances have been established by resolutions of the United Nations General Assembly, although some have been designated by UN specialized agencies.  The United Nations also observes anniversaries of key events in its history.

http://www.un.org/en/sections/observances/international-weeks/index.html