International Volunteer Day - December 5th
International Volunteer Day (IVD) is a chance for volunteer-involving organizations and individual volunteers to promote their contributions to development at local, national and international levels. By merging UN support with a grassroots mandate, IVD is a unique opportunity for volunteer-involving organizations to work with government agencies, non-profit organizations, community groups and the private sector.IVD was established by the United Nations (UN) General Assembly through Resolution 40/212 on 17 December 1985. Since then, governments, the UN system and civil society organizations have successfully joined volunteers around the world to celebrate the Day on 5 December.
Source: http://www.unv.org/what-we-do/intl-volunteer-day/