Let’s look at the beautiful moon.

This year’s Harvest Moon is September 15.

In the luni-solar calendar (note), the moon on the 15th day of the 8th month is called the “Harvest Moon.” In Japan it is also referred to as the “Potato Harvest Moon” in connection with agricultural events. The tradition of viewing the Harvest Moon is said to have been transmitted from China during the Heian Era.

This year’s Harvest Moon is September 15. Then 2 days later, at 4:05 on September 17, the Moon reaches full phase, so that the Harvest Moon and the full moon are separated by 2 days. The term “Harvest Moon” indicates the moon on the night 15 days after the moon passes new phase, while “full moon” indicates the moon at the moment when the Sun and the Moon lie in opposite directions as seen from Earth. Because the methods for determining them are different, differences in the dates can occur. Even though the last time that the Harvest Moon and full moon were 2 days apart was 9 years ago in 2007, the next time there is a 2 day difference is next year (2017).

In addition, the 13th night of the 9th month in the luni-solar calendar is known as “the 13th Evening.” In Japan, it is traditional to also conduct moon viewing on that evening. The 13th Evening moon is called “the Latter Moon,” “the Bean Harvest Moon,” or the “Chestnut Harvest Moon.” This year the 13th Evening falls on October 13.

(note) This calendar was used in Japan until the Meiji Era. The days of each month were determined based on the waxing and waning of the Moon.