Thirteenth Night, Otsukimi's lesser known pair

In 2025, today, November 2nd, is the moon viewing of the "Thirteenth Night". While Otsukumi, or the mid Autumn Festival as it is called in other Asian countries, is celebrated in several Asian countries, it is thought that "Thirteenth Night" is a custom unique to Japan. Otsukimi, was traditionally called "Fifteenth Night".

Most people don't seem to know that if you celebrate Otsukimi, which is traditionally called "Fifteen Night", you are also supposed to observe "Thirteenth Night". Only doing one (either Otsukimi or "Thirteenth night") is known as 片見月 katama-tsuki or ”one side viewing moon” and is considered bad luck. For the Thirteenth night, people offer edamame and chestnuts so the moon is called "Mame (bean) meigetsu" and "Kuri (chestnut) meigetsu".

It goes by the old, lunar calendar, not the Gregorian calendar which we use in modern times. It refers to the nights of September 13 - 14, by the solar calendar. Thus, by the Gregorian calendar the date changes each year. November 2nd is the latest date for "Thirteenth Night" in recent years. Most often, the date falls in October. For example, last year (2024) "Thirteenth Night" fell on October 15th and next year (2026) it will fall on October 23rd.