Double Ninth Festival is a traditional festival in China, which is celebrated on the ninth day of the ninth lunar month every year. The number of nine is the number of yang in the Book of Changes, and the number of two yang is heavy, so it is called Chongyang. Because the sun and the moon meet nine, it is also called double ninth. Returning to the truth of 1999, the ancients thought that 1999 Chongyang was an auspicious day. In ancient times, there were folk customs such as climbing mountains to pray for blessings, enjoying chrysanthemums in autumn, wearing dogwood, drinking alcohol to worship ancestors and praying for longevity. So far, it has added the connotation of respecting the elderly, feasting on the day of Chongyang, and being grateful for respecting the elderly. Climbing mountains and enjoying autumn and giving thanks and respecting the elderly are two important themes of today's Double Ninth Festival.
The Double Ninth Festival originated from the worship of astronomical phenomena, which began in ancient times, spread in the Western Han Dynasty and flourished after the Tang Dynasty. According to the existing historical data and textual research, in ancient times, there were activities of offering sacrifices to heaven and ancestors in season and autumn. Lu's "Spring and Autumn Season" and "Autumn Ji" recorded that the ancients offered sacrifices to gods and ancestors in September when crops were abundant, in order to thank them for their kindness.