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.
参考译文
每年农历正月十五是中国的元宵节。农历的第一个月称为元月，在古代夜晚又被称为“宵”，新年的第一次满月出现在元月十五，所以这一天就被称为“元宵节”。
新年伊始，圆月当空，根据中国传统，要挂出各式各样五彩缤纷的灯笼供人们观赏。与此同时，人们也会猜灯笼上的灯谜，然后吃着汤圆，全家人团聚在一起，其乐融融。