It is observed on 6th August annually. It marks the anniversary of the nuclear bombing on Hiroshima and Nagasaki. The primary purpose of keeping this day is to promote peace politics. The United States of America dropped an atomic bomb on Hiroshima’s city on 6th August in 1945; three days later, on 9th August, another nuclear bomb was dropped on Nagasaki.
The bombing on these two cities made Japan surrender unconditionally, and hence World War II came to an end. This was the first time any country had used a nuclear weapon to wipe out an entire city, and its repercussions were massive. The bombing on these two cities showed the devastating power of atomic weapons to the world