Article

Symposium on Calendars Used in Asia and Oceania

Yoshitaka HOJO*

This paper examines the problem of the calendar in the prehistoric society of theJapanese archipelago from the perspective of archaeology. The fundamental basis of thecalendar concept is to recognize the summer solstice and winter solstice and to consequentially recognize the vernal and autumnal equinoxes, and then incorporate them into thecalendar. Therefore, this paper investigates the relationship between the axial line of burialsites or ritual sites and the orientation of sunrise and sunset.
The head position of burial in the Jomon period is found within the range of the directionof sunset over the year. Therefore, it can be understood that prehistoric peoples acknowledged the summer solstice and winter solstice as the north–south limit point of the orientation of sunset.
In terms of the burial heads of royal tombs in the Yayoi period, it was established that theaxis of burial was aligned with the direction of sunrise on specific dates in the spring andautumn, and the agricultural calendar related to rice cultivation was restored. Furthermore,it can be argued that there was a possibility that the lunar calendar originated with thewinter solstice and the agricultural calendar was accordingly adjusted.
In other words, there was recognition of the summer solstice, winter solstice, springequinox, and autumn equinox in the prehistoric society of the Japanese archipelago, and it
reveals that a reasonably well organized calendar was in use even if it would be consideredsomewhat primitive to modern sensibilities.
Keywords
Burial Orientation, Directions of Sunrise and Sunset, Summer Solstice and Winter Solstice,
Sunrise Agricultural Calendar
Contents
I

Introduction
1 Natural environment
2 Social environments
II Orientation of the Jomon burial
1 Fujimoto’s discussion
2 Correction of the angle
3 Related examples
III A sunrise agricultural calendar restored froma royal tomb
1 Interpretation by Dairoku Harada

2 Analysis by the author
3 Comparative analysis with the Chinese
history book
4 The possibility that the actual calendar was
overlooked
5 The possibility that the movements of thesun and the moon were taken into
consideration
IV Conclusions* Tokai University

77

A Primitive Calendar Used by Prehistoric Farmers in JapanA Primitive Calendar Used by Prehistoric Farmers in Japanvery clear-cut. Based on this environment, it can be

I Introduction

pointed out here that prehistoric people had the sense ofThis paper considers prehistoric calendars in the号（２０２２）

Research Papers of the Anthropological Institute Vol.11 (2022)『人類学研究所 研究論集』第11

time required to divide a year into four parts.

Japanese archipelago from the perspective of archaeol-

It is most likely that the change of seasons was com-ogy. It may be said that it was a reckless attempt toprehended in connection with the movement of the sun

consider the calendar in prehistoric society in Japan,

and ancient peoples were sensitive to various changes inwhich was without characters.

the moon phases and tide levels and furthermore, they

However, since the origin of the calendar lies in thewould have understood a sense of time in relation to the

movement of the sun and the moon, if we can understandmovement of the sun and moon.

how ancient people recognized the movement of theseThis paper focuses on whether people of the Japanese

two planets, it is expected to provide a useful clue toarchipelago in the prehistoric period were aware of theconsidering the meaning of the calendar or the very idea

summer and winter solstices and the vernal or autumnalof time itself. Therefore, this paper focuses on the idea

equinoxes.

of orientation seen in extant burial and ritual remnants.

2 Social environments
1 Natural environment

Figure 1 shows the chronology of the theme of this

The Japanese archipelago belongs to the temperate

paper. The top is earlier historically, and the bottom is

monsoon zone and the changes in the four seasons arelater on in terms of time. This figure shows the corre-

Figure 1 Prehistoric Chronology of the Japanese Archipelago78

spondence between the prehistoric cultures of the

II Orientation of the Jomon burial

Japanese archipelago and the written records left by the

1 Fujimoto’s discussion

ancient governments of China and the Korean Peninsula.

In 1970, Hideo Fujimoto, a high school teacher inperiods of Japan can be divided into the Paleolithic

Hokkaido, published an important result of his research

period, the Jomon period, the Yayoi period, the Kofun

on burial positions in the Jomon culture. He excavatedperiod, and the Asuka and Nara periods.

74 burial sites at the Shizunai Gotenyama site and drew

An important precondition for considering the issue

a plan of the heads of their graves. It is clear from hisof the calendar is that people observed the movement ofanalysis that all burial heads face west, although they

the sun and moon at regular intervals. However, likely,

are spread out in a fan shape around the true west

this precondition does not work in the Paleolithic period(Fujimoto 1971).

when people were highly mobile. Therefore, the target

Fujimoto assumed that the direction of sunset shifts

periods of the present paper will be after the Jomon

throughout the year, and he derived the direction of theperiod, since ancient peoples in the Japanese archipelagosunset from the summer solstice to the winter solstice bystarted their settled life after that period.

using a simple method and applied it to the figure. As aresult, he found that most cases fall within the annual

Did people in the Jomon period recognize the summer

sunset range.

solstice or the winter solstice? To consider this issue,
this paper discusses the Shizunai Gotenyama site 静内御In modern Ainu customs, there is an idea that the

殿山遺跡, located in Hokkaido, which was a burial sitesouls of the dead follow the setting sun back into thein the Jomon period.

underground world. Fujimoto concluded that such an
idea goes back to the Jomon period.

In the Yayoi period, rice cultivation was brought into
the Japanese archipelago via the Korean Peninsula.

This diagram is also important in terms of the calen-

Furthermore, the state-level society of the Yayoi period

dar issues. It shows that Jomon people knew that thebegan to be partially described in the literature of

direction of the sun’s setting moved throughout the year.

ancient China, especially in Gishi-wajinden 魏志倭人伝

In other words, it can also be noted that they knew about(literally, an ‘Account of the Wa’ in “The History of thethe summer and winter solstices as the limit of theWei Dynasty”). The situation in Japan from the second

direction of sunset in a year.
However, this figure needs to be corrected. All

century to the third century is described in detail.
It is worth noting that there is a description stating

instances shown in the figure were measured at one

that people in the Yayoi period did not comprehend the

excavated site based on magnetic north. The direction ofcorrect calendar. However, it is necessary to compare

sunset on the summer and winter solstices was based on

this observation with the situation retrieved from thethe true north direction, and Fujimoto did not consider

archaeological records. As a source for considering thisthe change of the angle of ecliptic inclination. Because

problem, this article analyses the Hirabaru No. 1 Tombof this required correction, the position 17 burial heads

平原１号墓, located in the Fukuoka Prefecture. This site

fall outside the annual sunset range.

is very useful in considering the actual calendar used by

2 Correction of the angle

rice-paddy farmers in ancient times.
After the Kofun period (tumulus period), an advanced

Figure 2 shows the result of my correction of thecalendar was imported to the Japanese archipelago, andfigures created by Fujimoto. I corrected to the true norththe lunar–solar calendar was imported via Baekje 百済.

basis following the 1970 magnetic deflection angle. The

This paper focuses on the primitive calendar in the

thick line indicates the direction of the sunset for theearlier characterless society.

summer and winter solstices in 1500 B.C. The dottedlines show the northern and southern limits of the lunar
entry in the high moon mode of this period. Through79

A Primitive Calendar Used by Prehistoric Farmers in JapanThe date is shown on the left-hand side. The prehistoric

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Research Papers of the Anthropological Institute Vol.11 (2022)『人類学研究所 研究論集』第11

Figure 2 Bulial orientation at the Sizunai-Gotenyama site
Note: modified from Fujimoto 1971: 157

these adjustments, we can affirm the correctness of

The left figure is a reconstruction of a ritual structure

Fujimoto’s statement. It should be noted that the Jomon

found at the Sannai-Maruyama site 三内丸山遺跡 in thepeople were quite aware of the summer and winter sol-

Aomori Prefecture. One side of the structure’s axis is

stices as well as the northern and southern limits of theoriented toward the winter solstice sunset, while themoonset.

other side is aligned with the full moon’s rise from thenorthern limit, which occurs in cycles of 18.6 years.

3 Related examples

This is one case in the middle Jomon period.

According to our checking of the axis line of the

The right figure shows a ceremonial building found at

ancient ritual remains selected from the prehistoric

the Yoshinogari site 吉野ヶ里遺跡, in the Sagaarchaeological sites in the Japanese archipelago, 16 sites

Prefecture, surrounded by the mysterious shape of thematch the direction of sunrise of the summer or wintermoat and earthworks. The axis of this ritual area faces

solstice.

the direction of sunrise at the summer solstice. Because

The burial remains among these examples show clearof more detailed observation, it was revealed that thisevidence of aligning their axes with the direction ofaxis line also coincided with the direction of the coming

sunrise on the winter solstice. It can be presumed thatof the full moon of the northern limit, which appeared

people in each period chose the winter solstice as thenear the winter solstice. This is one example from thedate of funeral rites.

late Yayoi period.

Figure 3 shows two specific examples of ritual sites.

80A Primitive Calendar Used by Prehistoric Farmers in Japan

Figure 3 An instance in which the axis of the ritual site in the prehistoric period of the Japanesearchipelago coincides with the direction of the appearance of the full moon at the northernend of the winter solsticediameter of 46 cm, the largest ones among bronze

III A sunrise agricultural calendar restoredfrom a royal tomb

mirrors excavated in Japan, and many and various beads
were found in the tomb, dating back to around 150–180
A.D.

The Fukuoka Prefecture, which faced the Korean
Peninsula, was the center of Yayoi culture because rice

Harada estimated the burial head position and genderfarming culture was first developed in this special area.

of the buried person by the combination of burial goods

In the first century, the political organization in thisand their positioning in the coffin. The burial headregion gave tributes to the Later Han Dynasty in China

position faced west, and the buried person is assumed ato secure their position as kings. The Ito Province is one

woman. In addition, because of detailed observation of

example, and there is a strong possibility that thethe axis and direction of the burial, Harada noticed that

Hirabaru Tomb No. 1 would be the grave of a Queen of

there was a depression on a mountain called Hinata Pass

Ito from the late second century. This tomb was exca-on the extension line of the foot side. He also confirmed

vated by Dairoku Harada in 1965.

that the day when the sun rises from Hinata Pass is
October 20th. As the end of October coincides with the

1 Interpretation by Dairoku Harada

autumn harvest ritual, called Kanname-sai 神嘗祭,

Harada’s excavation revealed that the central body ofHarada estimated that the origin of the current shrine

the tomb consisted of a wooden coffin. Furthermore,

ceremony could be adjudged to go back to the burial

there were 40 mirrors, including five mirrors with arituals of the Princess of the ancient Ito state.

81

However, Harada’s understanding based on the myth

Focusing on the evening of both days, the shadow

of “photosensitive conception” of pregnancy under theextending from pole 2 just before sunset seems to

sun in the morning, with actual agricultural rituals, wasoverlap the pillar on the east side of the Torii. Such acompletely ignored by academic society at that time.

phenomenon cannot be considered simply an accidental

death, a re-excavation was carried out and important

intended it. When they stand at the Torii, it is also worth

discoveries were made around the tomb. The remains ofnoting that they could recognize that the days are close

four wooden posts and the remains of Torii 鳥居, theby the direction of the shadow extending from pole 2
toward the Torii at sunset (Figure 4).

sacred place in which people pray, were also found.

The east major pole discovered through re-excavationand this specific ritual is held from October 15 to 25.

is located on the line connecting with the central burial

February 21 is also an important date because the11site of Hirahara No. 1 Tomb and the Hinata Pass.

Sikinen-sai 祈年祭 is held at the Ise-jingu Shrine 伊勢神

Regarding this positional relationship, the first light of

宮 in spring to pray for a good harvest of rice of the year.

the sun rising from the Hinata Pass shines on the east

February 21 coincides with the period when this specificmajor pole and the shadow extending from the poleritual was held. In other words, the Sikinen-sai in spring

overlaps the central burial site. It can also be noted thatand the Kanname-sai in autumn are a pair of important

people in the Yayoi period observed a shadow extending

rituals, and it is important to note that they are consistent

to the center of the tomb from the Torii and used it as awith the sunrise agricultural calendar retrieved from thesunrise calendar. Based on this hypothesis, the author

Hirabaru Tomb No. 1.

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Research Papers of the Anthropological Institute Vol.11 (2022)

result; it is emphasized that the Yayoi people had『人類学研究所 研究論集』第In 1998, more than 10 years later after Harada’s

As Harada pointed out, October 22 of the 2 days

2 Analysis by the author

coincides with the holding period of the Kanname-sai,

A clear correspondence between the sunrise/sunset ofdetermined the dates when this phenomenon occurred as

the summer solstice and those of the winter solsticeFebruary 21 and October 22.

Figure 4 Sunrise Agricultural Calendar Reconstructed from Hirabaru Tomb No. 1

82

5 The possibility that the movements of the sun

ship between the shadows extending from these poles

and the moon were taken into considerationand the main sections of the tomb. Furthermore, it can

It is also possible that the sunrise calendar was

be pointed out that burial rituals here may have beenaccompanied by the act of observing the waxing andperformed at the winter solstice, because the central axis

waning of the moon. According to the Julian calendar,of the burial path located in the southeast coincides withthe winter solstice in the latter half of the second century

the direction of the sunrise on the winter solstice (Hojo

was generally December 22. There are 61 nights from2017, 2020).

December 22 to February 21. The error from the 2cycles of waxing and waning of the moon is 2 nights.

3 Comparative analysis with the Chinese history

From October 22 to December 22, there are 61 nights inbooktotal. On the other hand, the vernal equinox generally

There is an important text for estimating the results ofoccurs on March 20, and from February 21 to March 20,

these works mentioned above. The Chinese historicalthere are 29 nights or 30 nights in total, which roughly

document Gishi-wajinden 魏志倭人伝 mentions the cal-corresponds to the time of one cycle of phases of theendar used in the Ito state.

moon. Therefore, it is most likely that the dates of late
February and late October were set by the relationshipThe meaning of「魏略曰 其俗不知正歳四節 但計春耕

with lunar movement on basis of the winter solstice.

秋収為紀年」 is as follows: They do not know thesummer solstice or winter solstice, nor do they know theIt may be possible that Yayoi people vaguely consid-

correct division of the four seasons. However, they haveered the plowing in spring and the harvesting in autumn,

a one-year calendar made by measuring the cultivationand that they did not use a simple sunrise calendar, but

in spring and the harvest in autumn.

rather, set the reference to the end of the second round of
the moon phases starting from the winter solstice.

The underlined part is very important. The answer tothe question of what kind of measuring device it was canA high level of knowledge of the calendar should be

be interpreted as the special relationship of tomb andnecessary to determine the vernal and autumnal equi-

poles already discussed above. In the same way, thenoxes. Yayoi period people may have understood it bycorrespondence with the dates of the current shrineusing the phases of the moon. In other words, Yayoi

rituals in Japan can be also understood. Late February

people may have already used a calendar that divides

and late October are one pair of important terms for

one year into four seasons or six seasons.
Another possibility is that a circle was drawn aroundagricultural rituals in spring and autumn. It is still

the pole to mark the major sunrise shadows such as thevalued as the Ise-jingu Shrines’ ritual.

summer solstice and winter solstice. Such a circle was

4 The possibility that the actual calendar was

not observed in the excavation, but there is a distance ofoverlooked

15 m between the wooden coffin and the east major

The place where the Chinese envoys stayed,pole. If that device had been used, it would have beeneffectively an advanced sunrise anemometer.

described in the Gishi-wajinden 魏志倭人伝, should bealso discussed. The meaning of 「常亭伊都国」 is asfollows: The envoys from Wei who visited this land

IV Conclusions

were only allowed to stay in Ito state.
This sentence suggests that envoys from Wei were

As is indicated by the analysis, it is worth noting thatallowed to walk around freely in Ito, and that they mightprehistoric people in the Japanese archipelago recog-

have actually visited tomb. No. 1. It may also be possible

nized not only the Winter Solstice and the Summerthat they saw a sunrise farming calendar using shadows

Solstice but also the spring equinox and autumn equinox

from the poles, but those envoys overlooked the fact thatat an early point and understood them as the concept of

the Ito people knew both solstices very well.

a calendar.

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A Primitive Calendar Used by Prehistoric Farmers in Japan

should be pointed out based on examining the relation-

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Research Papers of the Anthropological Institute Vol.11 (2022)『人類学研究所 研究論集』第11

Figure 5 The peak of the sunrise at the vernal equinox seen from the Karako-Kagi site
and the early Kofun clusters with the mountain peak at the top of the picture

Figure 5 shows the scene of the sunrise at the vernal

is noteworthy that they recognized the vernal andequinox from the Karako-Kagi site 唐古・鍵遺跡, locatedautumnal equinoxes by the sun rising from this peak, theat the center of the Nara Basin in the Kinki region. Thissummer solstice by the sun rising from Mt. Takahashi inscene was taken from a large building which was

the north, and the winter solstice by the sun rising fromassumed to be a rice warehouse built in the third century

Mt. Miwa in the south. The annual sunrise calendar was

B.C., the first half of the middle of the Yayoi period, andbased on the sunrise from the main eastward ridge.
This site is a settlement of the Yayoi period. Forty-

the sun rises from the north peak of Mt. Ryuo 龍王山. It
84

seven early keyhole-shaped burial mounds were built on
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85

A Primitive Calendar Used by Prehistoric Farmers in Japan

set at the north peak of Mt. Ryuo and extended to the