The 15th day of the first lunar month is Lantern Festival, you should eat glutinous rice balls.
Tips
culture
正月十五 marks the Lantern Festival (元宵节), the traditional end of the Chinese New Year period. People eat 元宵 / 汤圆 (glutinous rice balls), watch lantern displays (赏花灯), and solve lantern riddles (猜灯谜).
usage
正月 is pronounced zhēngyuè, not zhèngyuè, an irregular reading specifically for the first lunar month.