Hi-no-Michi Calendar of Kanayama Megaliths

Six-season chart

Kanayama Megaliths and Observational Astronomy

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The Kanayama Megaliths are a set of three megalithic groups in Kanayama, Gifu Prefecture. They have only within the last twenty years been found to be a solar observatory for ascertaining the calendar of the tropical year. They determine the year so exceedingly well that their calendar is the most accurate in the world today. This calendar and this observatory have been in operation for five thousand years! Or more. 

Solar Calendar

The solar calendar incorporates the four-year leap-year cycle and the 128-year leap-year cycle. How does it do so with only solar observations? Aren’t most megalithic sites an arrangement of megaliths with alignments to the equinoxes and the solstices? Why are not the other sites in the world as accurate as the Kanayama Megaliths?

The answer lies in the theory and the practice of the Kanayama Megaliths. Even though we know that the sun rises due east on the equinoxes of spring and autumn, how do we determine exactly those dates? How do we determine the dates of the summer and winter solstices? Solstice dates are notoriously hard to determine due to the nature of solstice: the time when the “sun stands still.” In other words, the track of the sun in the sky varies very little from day to day around the time of winter or summer solstice.

The way around this is to take accurate measurements. How do you do that? You use the technique of measuring spotlight positions as functions of time.

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Spotlight observations.  The megaliths of Kanayama were designed and constructed so as to form two chambers of stone, called Senkoku-ishi and Iwaya-Iwakage. The megaliths forming each chamber were arranged to form a small opening where sunlight could enter. The entering sunlight would form a beam like a spotlight on an interior surface such as a flat stone or the floor of the man-made cave.

Hi no Michi

Daily the sun travels its path in the sky. It is called Hi no michi, a term which comes to us from long ago. In those days, Hi, the sun was highly respected. We thoughtlessly call indigenous people, “sun worshippers.” This is highly disrespectful to our ancestors who realized the importance of the sun as the giver of life. Even though we are speaking of the path of the sun in the sky, the term Hi may have really meant the Spirit of the sun, the life-giving energy of the sun. Remember that the word, michi, means literally “path” but the connotation is “proper path” or even “law.”

The modern term is taiyou no michi, where taiyou is the physical sun. Both expressions are used today, taiyou no michi being more technical and hi no michi more poetic.

Sun’s Path in the Sky.  The sun moves through a band in the sky. The northernmost limit of this band is the path traveled by the sun on summer solstice day. The southernmost limit is the path on the winter solstice. In the middle is the path of the equinox sun. This diagram shows the three paths during the half year it takes to go from summer solstice to winter solstice or vice versa. They divide the sun’s band into two sub-bands.


Yontobun of Kanayama Megaliths

Yontobun means “dividing into four parts.” The band of the sun’s path is divided into four parts, four unique periods of the year for making special observations of spotlights. The above two periods are divided — in the sky — into two equal parts each, making a total of four periods of the year. Those four periods are not all of equal duration.

Think of the year as having about 360 days. This is a good approximation to work with. After all, we divide the circle into 360 parts called “degrees.” Mathematically, the number 360 divides easily into four parts of ninety each, and six parts of sixty each. Agreed?

Sun’s elevation angle. There’s one thing you need to know about how the sun in the sky appears to us on earth. Its elevation angle in the sky varies over the year. It is described by a sine function which looks like this.

sine function

Why does the sun behave like this? That is just the way it is! It can be explained by physics and mathematics, and the sine graph is the result. If we take the highest peak to be the summer solstice day, the lowest valley is winter solstice day. The horizontal axis represents days and the vertical axis is the number of degrees above or below the norm at the equinoxes. The curve begins with spring equinox, then summer solstice at the peak, autumn equinox at the axis, and winter solstice at the minimum, ending with spring equinox once again.

Now, this is the crucial question. When will  the sun in the sky have an elevation angle that is halfway between the summer solstice and equinox elevations, and when halfway between equinox and winter solstice elevations? Look carefully at the chart. The answer, both mathematically and observationally, is sixty days before and after the solstices, and thirty days before and after the equinoxes. Think about it.

This fact seems to be little known amongst modern people who are not very good at observing nature (or at mathematics). People ordinarily divide the year into four equal parts by counting days: about 90 for each season, and divide each season into halves of 45 days. That’s fine if the objective is to divide by days. However, in Kanayama, the megaliths are designed to divide the sun’s path by angle in the sky. Aren’t they clever?

Yontobun is the basis of this unusual solar calendar and it is made possible by accurate spotlight observations.

Perhaps the ancient astronomers of Iwaya Valley had to be extra clever because they were challenged by being in a mountainous region!

The Kanayama Six-Season Year

The yontobun cycle of the year can be described as having six parts of sixty days each. This makes for a beautiful calendar of the year, as our chart shows. Observations at Kanayama Megaliths follow the six-season pattern. Starting with winter solstice at the bottom of the circular chart, we give the beginning dates for the sixty-day seasons for observations.

12/22  Late Winter

2/19  Spring

4/22  Early Summer

6/21  Late Summer

8/20  Autumn

10/23  Early Winter

Six-season chart

Kanayama Six-Season Calendar

(by Shiho Tokuda)

The spring equinox lies in the middle of the spring season, and the autumn equinox is in the middle of the autumn season. Summer solstice occurs between early and late summer, and winter solstice occurs between early and late winter.

Leap years.  The careful astronomer sees a slip in the solar events as the years roll by, and knows to add a day every four years to keep them on track. Furthermore, it is necessary to not add a day every 128 years (every 32nd leap year). These leap-year events are observed at Iwaya-Iwakage. Leap-year observations make this the most accurate operating calendar system in the world!



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