Each year there are four special days: They are the day of miracles, the day the Buddha was enlightened, the day the Buddha first taught the four noble truths, and the day he descended from the god realm of Tushita to Jambudvipa. There are six realms and in the human realm there are four great continents and eight subcontinents. The continent we live on is Jambudvipa.
According to the lunar calendar the first month is the miracle month. When Shakyamuni was forty, six great Hindu teachers, who represented the six schools of Hinduism that existed at the time, challenged Shakyamuni to a competition of miracles. At that time great kings and noble families sponsored teachers who could perform miracles. So Buddha accepted the challenge. He accepted because many would be benefited and achieve the arhat state and people of the future would be inspired to practice as a result of his demonstration. The first day to the fifteenth of the first month are precious and the fifteenth is especially great. The competition happened in the Bihar in India at Sravasti. 80,000 Buddhists and 84,000 Hindus attended the competition.
On the first day Buddha held his toothpick, put it on the ground and it turned to the wish fulfilling tree. It was decorated with jewels, like a Christmas tree. On the second day Buddha manifested two wish fulfilling jewels. The third day the king offered to wash Buddha's feet. When Buddha washed his feet, he threw the water and it became a pool with the eight special qualities of water. Whoever drank or touched it were healed. Today there is a well there where small amounts of water are offered for sale. It is useful for treating disease. On the fourth day it rained and the rain filled the eight canals. The fifth day Buddha emitted golden light from his mouth and people could see beings of the six realms being liberated. On the sixth day Buddha transformed some energy and everyone became clairvoyant and knew each others minds. On the seventh day Buddha manifested as the wheel turning king and many people converted to Buddhism. Up to that time the Hindu teachers had not shown miracles. On the eighth day the gods from Indra's palace sponsored the meals. They served Buddha and made offerings to him. Buddha's hand pressed the side of his seat and a thundering sound was emitted. Five frightening giant cannibals came out of the ground and they went for the seats of the Hindu teachers. Vajrapani also threatened the Hindu teachers. The Hindu teachers ran away. Vajrapani manifested a great storm. It became a tornado which picked up the Hindu teachers and their retinues and tossed them in the water. 60,000 Hindus converted that day and many monks attained the arhat's state and understanding. The gods showered flowers.
Some believe the eighth of the first month is the Buddha's birthday. Others believe the fifteenth of the fourth month is Buddha's birthday. Why do some believe the eighth. When Buddha dwelt at Sravasti, where he was for twenty four years, they were not allowed to build on the land were the monks camped The monks were required to live under a tree or in a small hut or tent. The land in Sravasti had three land owners. The land owner asked when is your birthday. Buddha replied in the first lunar month. Some marked his birthday then, according to the Vedic calendars.
The first to eighth day are the competition days. From the eighth to the fifteenth, Buddha showed miracles without competition. On the eighth day Buddha grew his body until the Brahma realm was under his chin. On the tenth day Buddha's body grew to the top of Akanishta. On the eleventh day, the Buddha he was not visible but the sound of his voice was heard everywhere. On the twelfth day light from his body radiated to all of samsara and developed loving kindness in all. On the thirteenth day Buddha manifested light from the spot between his eyebrows, filling all space with Buddhas, all who taught the dharma. On the fourteenth day the flowers that were offered by the gods filled all of space and on each flower a Buddha manifested and taught. On the fifteenth day Buddha gave the energy so that all beings could see all the six realms. Many people converted to Buddhism after seeing the lower realms with their own eyes. There are eight great stupas. One is called the miracle stupa and was built to commemorate this event. So that is the first great day., the day of miracles, from the first to the fifteenth of the first month. Tibetans celebrate the new year at this time.
"When the time came for the contest, the Buddha cast a mango seed on the ground; instantly the seed took root, and a great mango tree arose to shade the hall. After defeating the six philosophers and converting them to his teaching, the Enlightened One performed the Great Miracle of the Pairs.
"Standing in the air at the height of a palm tree, flames englufed the lower part of his body, and five hundred jets of water streamed from the upper part. Then flames leapt from the upper part of his body, and five hundreds jets of water streamed from the lower part. Then by his magic power, the Blessed one transformed himself into a bull with a quivering hump. Appearing in the east, the bull vanished and reappeared in the west. Vanishing in the west, it reappeared in the north. Vanishing in the north, it reappeared in the south. ... Several thousand kotis* of beings, seeing this great miracle, became glad, joyful, and pleased."
-Mahavastu (Buddhist scripture)
*A koti is equal to 10 million.
Now that's a pretty public series of miracles, eh?
P.S. Pass on this little nugget to the next person who tries to convince you that Buddhism is not a religion.