On December 11, 2014, the United Nations General Assembly declared the 21st of June every year to be International Yoga Day. India officially gave the proposal. 175 countries supported the resolution.
To read Swami Veda Bharati's Message for International Yoga Day, please use this link: http://ahymsin.org/main/swami-veda-bharati/message-for-international-yoga-day-june-21.html
To learn more about International Yoga Day, see: http://www.yogadaycelebration.com/
Many areas are holding events the weekend before. Check your local listings for the date and time of a public celebration near you.