Lǎohuà shuō, bùguò zhēngyuè shíwǔ nián jiù méi guò wán.
As the old saying goes, until you've celebrated the 15th, Chinese New Year isn't really over.
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.