The Year 660 BC for Emperor Jimmu's Accession Was an Ideal Designed by the Suiko Court through Dunjia

660 BC. This is the year in which Kamuyamato Iwarebiko, who had marched east from Hyuga, is said to have ascended the throne in Yamato, where Kashihara Shrine stands today. It is the so-called year of Emperor Jimmu’s accession.

Yet open the Nihon Shoki, and the figure 660 BC appears nowhere. All that is recorded is that on the first day of the first month of the year shinyu, the emperor ascended the throne at the palace of Kashihara. That is all. There is no Western calendar year and no absolute date. There is only the sexagenary cycle and the new moon, the movement of the moon. Moreover, the sexagenary cycle comes round every sixty years, so a shinyu year returns again and again, every sixty years. From this single line alone, in other words, one can never determine which shinyu year is meant.

Why shinyu in the first place? Behind it lies not an accurate number of history in our present sense, but an idea. And the basis of that idea is the chenwei of ancient China, its prophetic apocrypha.

In chenwei, the mandate of heaven is renewed in a shinyu year, sixty years make one era, and every twenty-one eras, or 1,260 years, a great revolution overturns the realm. This calendrical art of prophecy was regarded as dangerous in China and long died out there, but in Japan it lived on for nearly a thousand years, and it was institutionalized as the custom of changing the era name whenever a shinyu year came round.

The Meiji historian Michiyo Naka took this up. He began working on the theme around 1878, and he considered that the ninth year of Suiko (601) fell on a shinyu year, a landmark year in Japanese history, within a few years of which the calendar came into use and the cap ranks were established. He then thought that the shinyu year 1,260 years before 601 might have been set as the year of Jimmu’s accession.

Simply subtract 1,260 from 601, and you arrive at 660 BC. The trick, in fact, was no more than this.

Naka’s theory, however, though reasonable, is somehow unconvincing. Did Naka overlook something, or was he looking in the wrong place? It was Tadao Iijima who struck at this weakness from an entirely different angle.

Iijima was Japan’s foremost scholar of Chinese astronomy and calendrics. In his Nihon Jokoshi Ron (On the Ancient History of Japan), published two years after the defeat, the question he raised concerned not numbers but tools. Naka, in other words, saw only dates and events, the trap into which modern historians fall. Iijima saw that without an understanding of the tools needed to read them, the matter could not be deciphered. Versed as he was in Chinese astronomy and calendrics, Iijima began from the essential point that calendrics was not the calculation of numbers but a tool of those who govern.

What matters is that both the method of counting years by the sexagenary cycle and the computational system of chenwei were put in order in China only after the end of the Former Han (206 BC–AD 8). Prototypes had existed in China since remote antiquity, but it took a great many years for them to be systematized. From this standpoint, the figure 660 BC naturally has no basis on the Chinese side either.

The question, then, is when the tool of astronomy and calendrics reached Japan.

It arrived in 602, when Gwalleuk, a monk from Baekje, came to the court bringing books on the calendar and astronomy. The Nihon Shoki records that the court then had Otomo no Suguri Koso study “astronomy and dunjia” under Gwalleuk as his teacher. What caught Iijima’s eye was this dunjia.

Dunjia is a kind of divination that arose in the Later Han (25–220). The secret of secrets known as Qimen Dunjia survives to this day, but it does not tell fortunes by looking up at the stars. It moves numbers on a table. It supposes that Taiyi, the heavenly emperor and the root of all things in ancient China, travels through nine palaces, and from that arrangement it works out the character of a year. This art, inseparably bound up with the calendar, could be called “a technique for giving meaning to a year,” as opposed to “a technique for giving a year a number.” Interestingly, the lineage of Otomo no Suguri Koso, who mastered this secret art, later leads to the Tomo clan of Koga, the representative family that sustained the famous Koga-ryu ninja.

And it was precisely in the reign of Empress Suiko (593–628) that this art reached Japan. What is more, as noted above, 601, the ninth year of Suiko, was a shinyu year.

Three years later, in 604, a kasshi year, the Twelve Level Cap and Rank System was put into effect, the Seventeen-article constitution was established, and the first calendar in Japan was distributed. At first glance this seems a sudden burst of progress, but in fact it was promulgated by calculation. For in chenwei, the mandate of heaven is renewed in a shinyu year and the laws are renewed in a kasshi year. The new government of the Suiko court, in other words, understood this current and followed it, fitting itself to the very inch onto the chenwei calendar that runs from shinyu to kasshi. Those who carried out the new government were Soga no Umako and Prince Shotoku.

The power triangle of the Asuka period, Empress Suiko, Soga no Umako, and Prince Shotoku, deliberately aligned itself with the newest technology of the day in order to show off its new government as a great revolution. Its political acumen is impressive.

According to the Nihon Shoki, Jimmu’s accession falls in “the first year, shinyu,” and kasshi falls in “the fourth year of Jimmu.” Three years from shinyu to kasshi. Three years from the ninth year of Suiko to the twelfth. They follow exactly the same shape. What on earth does this tell us?

What Iijima showed, following the arrangement of dunjia step by step, was that Jimmu’s first year, shinyu, had been “placed” in a position that coincides exactly with the shinyu of the Suiko court. It was no coincidence. The founding myth was designed “politically” to overlap with the new government of the Suiko court.

The shinyu of Jimmu’s first year, in other words, was a projection back onto high antiquity, onto the first emperor Jimmu, made with the newly imported technique of dunjia in order to declare politically that Empress Suiko’s new government was a radically new age. It was an idea, not a historical fact. This was Tadao Iijima’s conclusion.

But he did not stop writing there. Simply dismissing it as unhistorical would have been easy, but what he went on to write was, in substance, the following.

That story sets forth the ideals of Japan’s new government. The stories of high antiquity are things whose ideals we ought to grasp, and anyone who studies the history of Japan must pay close attention to this one point above all. “Ideal” sits better if we call it “thought.”

Sadly, Iijima’s words did not reach the historians who came after him. Postwar historians came to chase nothing but numbers, and with the occupation forces having banned moral education, history was stripped of thought and spirit alike and became a hollow list of dates and events. In this way, the history that had once fascinated so many Japanese turned into the most tedious cramming for entrance exams, and the people lost interest in it.

660 BC is not something that actually happened. It is a blueprint in which rulers of the seventh century, who had nothing to do with Emperor Jimmu, buried in the deepest layer of time the ideal they held of what their country ought to be. This “reaching back” is quite hard to grasp for people today, who have been equipped with the Western linear time of past, present, and future. Yet this method of reaching back is precisely Japan’s method of nonlinear time, and it leads directly to the later Kojiki and Nihon Shoki.

What comes into view once we acquire this method of reaching back? The world of myth contained in the Kojiki and the Nihon Shoki.