Question

At what year emperor Ashoka changed into buddha

Answer 1

After the lethal war of Kalinga

Answer 2

one particular battle resulted in such loss of life that Asoka was filled with remorse for what he had done. This event caused him to undergo a spiritual transformation that would be instrumental in the spread of Buddhism. Asoka not only personally converted to Buddhism (which he had learned about from a monk), he applied Buddhist principles to the way he ruled his empire.