Prime Minister Narendra Modi on Sunday said that June 21 not only marked the start of an annual day commemorating yoga, but it was also the start of new era for training the human mind for peace and cordiality.Speaking at a function marking the start of International Yoga Day here at the Rajpath, Modi said that yoga is not only an exercise to make the body flexible but a path for inner development."It marks new era of training of human mind for peace and cordiality," said Modi who wore a white full T-shirt.About 37,000 people are taking part in the yoga programme on the Rajpath.