The 15th day of the 1st lunar month
The 15th day of the 1st lunar month is the Chinese Lantern Festival because the first lunar month is called yuan-month and in the ancient times people called night Xiao. The 15th day is the first night to see a full moon. So the day is also called Yuan Xiao Festival in China.
According to the Chinese tradition, at the very beginning of a new year, when there is a bright full moon hanging in the sky, there should be thousands of colorful lanterns hung out for people to appreciate. At this time, people will try to solve the puzzles on the lanterns and eat yuanxiao (glutinous rice ball) and get all their families united in the joyful atmosphere.
The third story about the origin of the festival is like this. Buddhism first entered China during the reign of Emperor Mingdi of the Eastern Han Dynasty. That was in the first century. However, it did not exert any great influence among the Chinese people. one day, Emperor Mingdi had a dream about a gold man in his palace. At the very moment when he was about to ask the mysterious figure who he was, the gold man suddenly rose to the sky and disappeared in the west. The next day, Emperor Mingdi sent a scholar to India on a pilgrimage（朝圣）to locate Buddhist scriptures. After journeying thousands of miles, the scholar finally returned with the scriptures. Emperor Mingdi ordered that a temple be built to house a statue of Buddha and serve as a repository for the scriptures. Followers believe that the power of Buddha can dispel darkness. So Emperor Mingdi ordered his subjects to display lighted lanterns during what was to become the Lantern Festival.