Step 1: Significance of International Yoga Day.
The United Nations declared June 21 as International Yoga Day in 2014 after a proposal by India's Prime Minister, Narendra Modi.
Step 2: Objective of Yoga Day.
This day is celebrated globally to promote the importance of yoga for health, wellness, and mental peace.
Step 3: Conclusion.
Thus, International Yoga Day is celebrated on June 21, making option (2) the correct answer.