In January 2004, Iranian Nobel laureate Shirin Ebadi had taken a proposal for an International Day of Non-Violence from a Hindi teacher in Paris teaching international students to the World Social Forum in Bombay. The idea gradually attracted the interest of some leaders of India’sCongress Party (“Ahimsa Finds Teen Voice”, The Telegraph, Calcutta) until a Satyagraha Conference resolution in New Delhi in January 2007 initiated by Sonia Gandhi and Archbishop Desmond Tutu called upon the United Nations to adopt the idea.
On 15 June 2007 the United Nations General Assembly voted to establish 2 October as the International Day of Non-Violence. The resolution by the General Assembly asks all members of the UN system to commemorate 2 October in “an appropriate manner and disseminate the message of non-violence, including through education and public awareness.” 
The United Nations Postal Administration in New York City prepared a special cachet to commemorate this event, following a request from the Indian Ambassador at the Permanent Mission of India to the UN. The boxed pictorial cachet design was prepared by the UNPA and was limited to cancellation at UNPA’s NY location (not Geneva and Vienna). The UNPA has indicated that all outgoing UNPA mail between October 2 and 31 carried the cachet. Information on various philatelic material carrying this cachet is summarized at a website dedicated to Gandhi philately and can be accessed here.