The General Assembly declares 4 to 10 October World Space Week to celebrate each year at the international level the contributions of space science and technology to the betterment of the human condition (UN General Assembly resolution, 6 December 1999.) The choice of dates was based on recognition of two important dates in space history: the launch of the first human-made Earth satellite, Sputnik 1, on October 4, 1957; and the signing of the Outer Space Treaty on October 10, 1967. Since its United Nations declaration, World Space Week has grown into the largest public space event on Earth. More than 1,800 events in 73 countries.
World Space Week is the largest annual space event in the world. A total of 1874 events were registered for WSW2015.
As explained on the “How to organize a World Space Week event” pages, really any activity related to space or astronomy in the 4-10 October timeframe will count as a World Space Week event. It can be a small private activity at your local school, a lecture evening at your company, a special exhibition at your science center, museum, church, school or community center, a radio, TV or online event or a large scale public event at a national stadium, related to space, astronomy, sci-fi, rocket science or space-related science or technology.
Source: un.org | worldspaceweek.org