The Chrysanthemum Festival-- also known as the Choyo no sekku 重陽の節句 or the "double nines" on the Ninth Day of the Ninth Month, during the time of white dewdrops.
According to i ching philosophy, the doubling up of the odd, or yang numbers 1,3,5,7,9 was seen as auspicious, so that in Japan there are major holidays occurring on January 1st, March 3rd, May 5th, July 7th and September 9th. These "double yang" holidays were days of both celebration as well as purification and abstinence.
In ancient China, the ninth day of the Ninth Month was considered to be the seasonal marker of the “first chill of Autumn.” It was thought to be particularly potent because of the belief that the number nine, being the highest odd number (yang) from one to ten was especially lucky, and therefore this day with its “two nines” (that is, Ninth Day of the Ninth Month) was considered to be the ultimate in propitiousness.
Here is a poem I love by Li Qingzhao (My translation, so please tell me if you find any mistakes!)
醉花陰ー重陽
薄霧濃雲愁永晝,瑞腦消金獸。
佳節又重陽,玉枕紗櫥,半夜涼初透。
東籬把酒黃昏後,有暗香盈袖。
莫道不消魂,簾卷西風,人比黃花瘦
Drinking Wine in the Shadow of Flowers-- the Chrysanthemum Festival
Light mists and thick clouds,
The afternoon stretches on in sadness
Sweet incense rises from a golden brazier (keeping steady time)
On this auspicious festival of the Double Nines
As evening falls, the chills slips between the silken curtains onto my porcelain pillow, like jade
Sipping wine that evening—there by the eastern fence
The fragrance of the chrysanthemums filling my sleeves, quietly
How can I not be distraught?
The autumn wind fills the curtains
I have grown thinner than the chrysanthemums.
Li Qingzhao--longing for her husband who was faraway on business, spent the day in bed-- drinking wine and composing poems, in the shadow of the flowers by the eastern fence (採菊東籬下).
It is said that when her husband read it, so impressed was he that he vowed to not leave his room until he had composed a poem back of equal perfection. Refusing all food and all visitors for three days, he composed poem after poem. Later, he would incorporate her words with words of his own in a poem that a friend would remark that, "there are only three good lines in this one" (and those three good lines were, of course, the ones he had borrowed from his wife's masterpiece!)
For more on the double nines, please see Everything I have ever heard about Chrysanthemums (重陽の節句)
I felt the catch of the double-nines when I wrote the date today. And now I know even more about why! To say nothing of "chrysanthemum dew" . . . And, gorgeous translation and poem!