Beautiful moon in the 13th night 2017/11/2

In Tokyo we could enjoy beautiful and clear moon last night. It was 13^th night of 9^th month by lunar calendar. It is a traditional prevailing custom in Japan to cerebrate the moon of 13^th night of 9^th month as lively as the big cerebration of the 15^th night of 8^th month.

It is popular in the world to enjoy beautiful moon in the 15^th night of 8^th month by lunar calendar but to enjoy 13^th night month is unique custom in Japan.

By lunar calendar one month is composed of 29 days or 30 days. If the moon travels on perfect circle with constant speed, full moon should falls on 14^th or 15^th night. However the moon travels actually on ellipse circle with unstable speed. Therefore full moon moves from 13^th night to 17^th night.

With more than 40 % possibility, we can expect full moon in 15th night while it is only little chance to have full moon in 13^th night. People know they can’t expect full moon in that night but they are prepared to enjoy insufficient full moon or unfinished full moon.

It is common tendency for Japanese to prefer unfinished situation rather than perfect or completed situation.

It is time of harvest of agricultural products and various chestnuts. It is also the best season to watch moon shining in the clear autumn sky, with a variety of autumn harvests.

　moon in 13th night