13th. September in old calender is 十三夜【Thirteen-Night Moon🌔】which is not full moon but lucking little in Japan.

In Japan, 13th.September in old calender is called 後の月見【NOCHI NO TSUKIMI】or “Late Moon Viewing”（This year, it is 8th.October）.

Usually, people  watch 十五夜【JYUUGO-YA（fifteenth night）🌕】 full-moon while Late moon viewing  is 十三夜【JYUUSAN-YA】”thirteenth night” moon 🌔.

It is said that only once moon viewing a year is called 片見月【KATAMI-TSUKI】;”one side viewing moon” and it is not good fortune.

Emperor 宇多【UDA】 started the habit of  thirteen night moon viewing in 平安【HEIAN】 period about 1200 years ago.

Japan has tradition to love not perfect, incompleted things too☺️

There is a word “things become full, it would be lack” and old Japanese peoples sometimes disliked make things perfectly.

For examle, 日光東照宮【NIKKOU EAST LIGHT SHRINE】made by 徳川家康【TOKUGAWA IEYASU】1st. 将軍【SHOUGUN】in EDO period did not comleted it by lacking one part intendedly and prayed it would be existing eternaly.