Why 21st?
June 21st marks the transition of Sun from Uttarayana to Dakshinayana. This is the day Lord Shiva supposed to have first taught to his disciples according to Aagamas. Hence June 21st is the Birthday of Yoga. Lord Shiva taught 84.000 asanas to his consort Parvati, according to Hatha Yoga Pradeepika.
What is yoga?
Integration of body, mind and intellect with the Self/Atman. All the exercises is for that.
Today Bharat has ascended to the status of JagatGuru again.
India never conquered any countries/nations with a sword, but by spirituality & yoga spreading the message of peace & love she has always conquered the world and will continue to conquer.
Vande Maataram !! वन्दे मातरं
pic from www.gitamritam.com