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.