日本の旧暦に宿る歴史の知恵Historical Wisdom in Japan's Traditional Calendar

The Obon festival I mentioned yesterday, after the adoption of the solar calendar in the Meiji era, was long observed differently in each region depending on whether it followed the lunar calendar or the new calendar, but today it generally falls between August 13 and 16, and as one of the multi-day events for ancestral memorial rites, it came to Japan via India and China and was historically formed into a uniquely Japanese custom. When this time of year arrives, the heat of summer begins to ease slightly at night, and this is because it is just past Risshu (立秋, the “start of autumn” in the traditional calendar). In the lunar calendar, Risshu falls on the 14th day of Minatsuki, which in 2025 was August 7. As the characters in its name suggest, Risshu marks the beginning of autumn, yet in truth, in recent years it has become difficult for residents of urban areas along the Pacific coast of the Tokaido region to actually feel this seasonal shift.

I recall that when I was traveling in pursuit of summer festivals in the Tohoku region, once the festivals ended and night fell, the wind was already so cool that it made me feel autumn’s arrival. Across Japan, once the summer festivals and the Obon period are over, Shinto rites for the deities and ancestral memorial services come to an end, and preparations for the real autumn begin in earnest. In Japan, the lunar calendar was originally an agricultural calendar designed for farmers and was closely tied to their lives, and this current period is essentially the last moment to catch one’s breath before the busy harvest season.

However, with the intense climate change of recent years, and particularly with this summer’s prolonged lack of rain, there are concerns that the autumn harvest may fall short compared to average years. For farmers, there is also another unavoidable seasonal factor at this time: the “Two-Hundred-Tenth Day” (二百十日) in the traditional calendar. This typically falls around September 1, but in 2025 it will be on August 31. Since ancient times, the days around this date have been said to bring the strongest winds and the highest frequency of typhoons, making it the most worrisome and critical period of the year for farmers due to the frequent damage to crops.

It is also wise to avoid traveling during this time. Most people today no longer pay attention to the traditional calendar, yet it remains a crystallization of historical wisdom, and the points of caution it offers are as valid now as in the past. The week surrounding the Two-Hundred-Tenth Day is said to have the highest number of typhoons, meaning that travel plans often fail to proceed as scheduled. Those who understand this old knowledge will never travel during this period. And this is not just an old superstition—traditionally, communities across Japan held festivals to pacify the wind deity during this time. Today these events are no longer held at the village level, but the famous “Owara Kaze no Bon” in Toyama Prefecture is a surviving example. I once visited this festival out of interest, and it is important to note that it, too, originated as a rite to calm the wind deity.

Countless travel websites and blogs fail to mention such matters, but in fact one of the most important tips for traveling in Japan is to understand the traditional calendar, and to base your plans on it. Successfully navigating this “wind season,” when travel schedules are particularly difficult to coordinate, is what allows you to be fully prepared to welcome the magnificent autumn. Yet in recent years, typhoons have not been limited to this period, occurring frequently in atypical seasons, making them harder to predict. In other words, in present-day Japan, travel plans must always account not only for typhoons but also for earthquakes and all manner of natural disasters. Many travelers do not think this way, and for people from countries with no experience of earthquakes or typhoons, the concern may be hard to imagine, but earthquakes can occur at any time, and typhoons certainly do not arrange themselves conveniently around one’s travel plans. Considering also the frequent landslides and floods, it is clear that in order to enjoy traveling in Japan today, one must hone survival skills and always be fully prepared for emergencies. In a country like Japan, where natural disasters have always been frequent, such awareness is indispensable, and with weather forecasts increasingly unreliable, you must also be prepared to adapt your means of transportation to sudden heavy rains that can strike without warning.

Seen in this light, deciphering the traditional calendar and visiting the traditional festivals and customs that have been practiced in Japan for centuries can deepen one’s understanding of the country. It is also essential to seriously consider that we are now entering the final era in which most of the traditional customs and folk practices inherited through village communities are on the verge of complete extinction. Japan’s super-aged society will, by 2030, see more than 30% of its population over 65 years old—a first in human history for a nation of this scale—and apart from the United States, other advanced nations face the same challenge, so now is the time to understand what the future of one’s own country may look like through the lens of Japan. Even countries with a currently vigorous younger generation will ultimately follow a similar path, and thus understanding now what Japan has failed to do is essential for preserving culture into the future. As common sense dictates, cultural continuity cannot begin without people.

Personally, I believe that our generation may be the last that can still experience the culture that so many people think of when they hear the word “Japan.”