The 9th day of the 9th lunar month is the traditional Chongyang Festival, or Double Ninth Festival, which falls on Oct 7 this year.

In an ancient and mysterious book Yi Jing, or The Book of Changes, number "6" was thought to be a Yin character, meaning feminine or negative, while number "9" was thought to be Yang, meaning masculine or positive. Therefore, the number nine in both month and day create the Double Ninth Festival, or Chongyang Festival.

Chong in Chinese means "double." Also, as double ninth was pronounced the same as the word to signify "forever", both are "Jiu Jiu", Chinese ancestors considered it an auspicious day worth celebration. That's why ancient Chinese began to celebrate this festival long ago.

Here are 6 things you may not know about Double Ninth Festival.