Japanese seasonal time system

Introduction and Brief History

The new government decreed the abolishment of the old seasonal time system in 1872 to modernise the country. They adopted the Western time system, the fixed time method. Thus, all of the traditional Japanese clocks, wadokei, became obsolete, and the artisans of making wadokei lost their jobs.

Until then, Japanese people used a seasonal time system.

This time system divided a day into two: day and night. Plus, each day and nighttime was divided into six toki.

Each toki is approximately two hours in the Western time system, but it varies about 40 minutes at maximum depending on the season. This seems to be inconvenient these days; however, for the people in the Edo period, it was quite reasonable and convenient for them. As I mentioned in the previous chapter, they lived by the sun. Since most of them were farmers, that's enough.

However, this unique system was not adopted from the beginning of Japan.

In 671, the Emperor Tenji (626-672) made the first Japanese clock, rokoku, which used falling water to determine the time.

Emperor's staff rang a bell to tell the exact time to the staff of his government. 

It was June 10, so it is now celebrated as a commemoration of the time day. The employees of SEIKO, CITIZEN and other companies celebrate this day.

However, the bell was able to be heard in the Imperial Palace only, and the time was not publicly open to citizens. 

The end of the aristocratic government, of which the centre was the imperial system, led to the end of the fixed time system. After that, Japan gradually moved into a seasonal time system.

In 1185, marked by the Imperial authorisation to appoint shugo and jito (military governors and estate stewards), which effectively established the Kamakura shogunate. This is the end of the aristocratic era and Japan's feudal system with samurais began .

It is crucial to note the unique political structure surrounding the Emperor and the court aristocracy in Kyoto. 

While the Emperor remained the ultimate source of legitimacy and political authority, he acted largely as a figurehead, entrusting actual governance to the samurai class. This dual structure—separating symbolic authority from executive power—distinguishes the Japanese system from European, Chinese and other countrys' feudalism. Even in the late Edo period, the Tokugawa shogun derived his legitimacy from being formally appointed by imperial decree to govern Japan.

This political dual structure is quite different from the European and Chinese feudal system and still exists in modern constitutional monarchy in Japan. The only exception was during the Meiji to Showa period before the war. The emperor himself had sovereignty and directly controlled his government. However, he usually delegated the actual politics to his ministers and tried to refrain from talking about politics like the British king. 

National Isolation of Japan

Ieyasu's predecessor, Toyotomi Hideyoshi (1537–1598)—who governed whole Japan for the first time after the Japanese Civil War era(1467-1590 or 1615, opinions vary)—was deeply concerned about the influence of Christianity. In 1587, he placed Nagasaki, one of Japan's principal trading ports, under the direct control of his regime and expelled European, particularly Portuguese, priests.

The next ruler, Tokugawa Ieyasu, followed suit. He feared the spreading of Christianity might not only destabilise his regime but also lead to Japan's colonisation by European powers and the enslavement of Japanese people. In 1612, he issued a formal decree prohibiting Christianity, and subsequently severed diplomatic relations with Spain in 1624.

Historically, under the 1494 Treaty of Tordesillas between Spain and Portugal, Japan fell within the Portuguese sphere of influence. Firearms(teppo) were introduced by Portuguese visitors in 1543, while Christianity was brought in 1549 by Spaniard Francis Xavier (1506–1552), who acted as a special envoy under the patronage of the Portuguese government at the time.

Finally, the third Shogun, Tokugawa Iemitsu (1604–1651, reign: 1623–1651) banned Portuguese ships in 1639 and transferred the Dutch trading post to Dejima in Nagasaki in 1641. Dejima was completely isolated from the mainland and placed under the strict control of the Nagasaki Magistrate, which was commissioned by the shogunate.

This marked the completion of Japan's policy of national isolation (sakoku). This prolonged isolation had profound consequences for politics, foreign diplomacy, technology, culture, society, and the Japanese psyche itself. Even today, a certain underlying xenophobia or reservedness persists—a sentiment often echoed by foreign visitors and residents who remark, "The train was packed, yet the seat right next to me remained vacant..."

As for timekeeping, mechanical clocks had been imported by European merchants prior to the isolation. These foreign clocks ultimately served as the foundation for the evolution of Japan's domestic clocks, wadokei.

Japan's Seasonal Time System and Wadokei

Like the earliest European clocks, the traditional Japanese wadokei features only a single hand to indicate the time.

The dial shown here is a typical wadokei with evenly spaced intervals for each toki (time period). As mentioned earlier, because daytime and nighttime hours varied in length, the single hand moved at different speeds depending on whether it was day or night. While some rare wadokei clocks featured variable, uneven spacing on their dials so that the hand moved at a constant speed throughout the entire 24-hour cycle, these were quite uncommon.

The time cycle begins at 12:00 midnight. The first Japanese toki is Ne (子), which means "Rat" and is the first sign of the Chinese zodiac. This is followed by Ushi (丑 - Ox) and Tora (寅 - Tiger). For further details, please refer to Table 1.

Curiously, the numbers indicating the hours begin strangely at 9, followed by 8, 7, and so on, ending with 4 around 10:00 AM (and repeating the descending count for the afternoon/night cycle). The exact reason for this remains obscure, and there is no definitive explanation.

Interestingly, 12:00 noon corresponds to Uma (午 - Horse). The modern Japanese word for midday, shogo (正午), originates from this time system, where go (not long gō, but short go) is the Sino-Japanese reading for Uma.

Furthermore, children in Japan often eat an afternoon snack at around 3:00 PM, which is called oyatsu (おやつ). This word comes from the old practice of referring to this time slot by the eighth hour of the old clock system (o-ya-tsu, meaning "eight" in an older/polite counting form).

Similarly, you may have heard the expression Ushi-mitsu-doki (丑三つどき). This time is famously referred to as the hour when ghosts appear in the middle of the night. As shown below, the Ushi hour spans from 2:00 to 4:00 AM.

Interestingly, the "three" (mitsu) in this term does not refer to the third toki.

Because a single toki—lasting approximately two hours—was too broad a unit for everyday affairs, each toki was practically subdivided into four equal parts. While these quarter-segments lacked distinct individual names, each was equivalent to roughly 30 minutes. 

A famous example of this system survives in the term Ushi-mitsu-doki (丑三つ時). This refers specifically to the third 30-minute quarter of the Ushi (Ox) toki, translating to around 2:30 AM......Beware—this is when ghosts haunt!

Intriguingly, while everyday life relied on these four quarters, the fine divisions actually engraved on the wadokei dial split each toki into ten equal parts rather than twelve. Mathematically, a duodecimal (12-part) system would seem more compatible with a four-part division, yet Japanese makers opted for a decimal layout. The reason for this choice remains something of an enigma, but it aligns with a broader historical pattern: unlike the traditional British system based on twelve, traditional Japanese weights and measures frequently favored decimal counting like the French metric system.

SEIKO issued and distributed this quartz wadokei to their dealers in 1981 to commemorate its centenary.

This modernised wadokei clearly shows both Japanese seasonal time and Western time. It currently displays 8:05 AM.

SEIKO was established by Kintaro Hattori (1860–1934) in 1882. While Hattori never manufactured traditional wadokei during the Edo period, the roots of SEIKO connect deeply to Japan's horological history. For more details, please see SEIKO history.

My late father ran a small clock and watch shop and this piece was given to him by SEIKO.

Daily Lives of Japanese People in the Edo Period

The most important times of the day were 6-mutsu toki. In the traditional Japanese seasonal time system, two numbers—both called 6—marked dawn and sunset. These special hours were known as Ake-mutsu (dawn 6) and Kure-mutsu (sunset 6), respectively.

People would wake up to the bell of Ake-mutsu and return home at Kure-mutsu.

Because the sky begins to brighten well before actual sunrise, waiting for the exact moment of sunrise would waste daylight. Therefore, the Ake-mutsu bell rang approximately 30 minutes before sunrise. Similarly, the Kure-mutsu bell rang about 30 minutes after sunset, when darkness was nearly complete. As a result, the calculated daytime was longer than nighttime.

Outside of major cities like Edo, only the Ake-mutsu and Kure-mutsu bells were rung. For people living in rural areas, this was quite sufficient for daily life. Since the majority of the population were farmers working under the sun, knowing dawn and sunset was all they needed.

However, in Edo (modern-day Tokyo), bells were struck every single toki (roughly two hours)—even in the middle of the night. This was because many samurai serving the Tokugawa Shogunate were required to keep strict track of time. These toki was defined and noticed by wadokei settled in Edo castle. 

The Transmission of Time Information Across Edo

The time defined within Edo Castle was systematically transmitted and propagated throughout Edo. High-ranking officers in the Tokugawa shogunate government in the Edo Castle relied on this to notify their subordinates of the official hours, summoning them for administrative duties, meetings and official communications.

Within Edo Castle, there were specialists known as One survived O-Tokei-Shi (御時計師), who operated and maintained the complex mechanics of wadokei. Alongside them stood the official shogunal timekeepers, O-Tokei-Bozu (御土圭坊主), who were charged with managing timekeeping inside the castle. Every toki, time signals were propagated via bells(Kane 鐘) and drums(Taiko 太鼓) within the castle grounds.

In other cities, like Kyoto, Osaka and Nagoya, they had the same bell relay throughout their city centered on the castle.

The Bell Relay Network of Edo

While the sound of a bell travels far, its acoustic range is practically limited to a radius of roughly one kilometre. To ensure that time was thoroughly communicated to samurai bureaucrats and the citizens of Edo alike, a sophisticated relay system of time-bells (toki-no-kane) was established across the city.

The primary signal originated from the bell tower (kanetsuki-dō  鐘撞堂) in Honkoku-cho, which rang out the official time for the first time in Edo. This was operated by the civilian Tsuji family.

The sound of the Honkoku-cho bell was relayed outward across the city in a vast acoustic network:

Kane-tsuki-do in Honkoku-cho

Kan'ei-ji Temple in Ueno

Sensō-ji Temple in Asakusa

Honjo-Yokohori 

Hachiman Shrine in Ichigaya

Zōjō-ji Temple in Shiba

Jōman-ji Temple in Akasaka

Mejiro Fudō-son Temple in Ikebukuro

And finally, Tenryū-ji Temple in Yotsuya

Similar bell-relay networks operated in other major urban centres such as Kyoto, Osaka, and Nagoya, with each city's timekeeping system centered around its respective castle.

The location of these bells are shown on the map shown below. 

Please note that Ichigaya was unique because its time-bell was installed inside a Shinto shrine, whereas the other bells were located at Buddhist temples.

Before the Meiji Restoration, Shinto and Buddhism were syncretized (Shinbutsu-shūgō 神仏習合). Even today, shrines and temples often share the same grounds, and people naturally revere both. This reflects a unique Japanese approach to religion. Can you imagine believing in Christianity and Islam simultaneously?

At the heart of this tolerance is an animistic worldview: the belief that all things, including nature and inanimate objects, possess a spirit or life force. In Japan, countless deities (Yaoyorozu no Kami 八百万神) dwell all around us, observing our daily lives. The mythical yet natural worlds depicted in My Neighbor Totoro and Spirited Away closely capture this traditional Japanese perception of reality.

While Japan did experience religious conflicts—such as the persecution of Christians during the Edo period—these were primarily political measures by the ruling power to maintain sovereignty. Japanese religious tradition has historically prioritized harmony, coexistence, and integration over strict exclusion—a perspective that may offer valuable insights for our modern world.

Reference: Urai Sachiko, S. (2000). "A Research on Toki-no-Kane in Edo", Doctoral thesis, Japan Women's University

Who were the O-Tokei-Bozu?

The suffix bōzu denotes a Buddhist monk. True to their title, Otokei-bozu and other Bōzu officers shaved their heads and wore clerical robes.

Within Edo Castle, they served as high-ranking officials who assisted in the daily affairs of the Shogun. Moreover, they acted as vital liaisons, communicating with daimyos and transmitting direct orders from the Shogun.

Uniquely, they held the privilege of entering even the private quarters of Edo Castle freely—access denied to many of the even Shogun's closest attendants. As a historical aside, it is a fascinating and uniquely distinct characteristic of Japanese history that, unlike many other ancient imperial courts around the world, especially China and Korea, there were no eunuchs in Japan.

Japan's Special Seasonal Divisions: Nijuu-Shi-Sekki (Nijuushisekki二十四節気)

Also, the Japanese seasonal time system had to be adjusted quite frequently, because the length of a single toki varied continually with the movement of the sun. If this was neglected, the clock would quickly fall behind or run too fast.

In Japan, in addition to the four conventional seasons, the year is divided into 24 smaller seasons known as nijuushisekki, or the twenty-four solar terms.

This traditional system is still used in modern Japan—even weather forecasts frequently refer to them.

It is often said that each wadokei had to be adjusted in accordance with the nijuushisekki (the twenty-four solar terms).

It is often said that a clock operator had to adjust the clock in accordance with the nijuushisekki, roughly once every two weeks. However, this is not true. They actually had to adjust the clock much more frequently to accurately match the solar time.

The nijuushisekki are detailed in Table 2.

Table 2 Nijuushisekki     source: Mody, "A collection of Japanese clocks" (1932) and revised by site owner

The Guild System and Early Division of Labour

Within the early stages of Japan’s economy and domestic handicraft industry, a subtle form of manufacture and division of labour was already taking shape. The clockmaker's craft was largely hereditary; artisans learned the trade through strict apprenticeships under their fathers, passing down specialized knowledge through generations. Their work was primarily commissioned by daimyō (feudal lords) and wealthy merchant patrons.

It is worth noting that while a subtle transition from domestic handicraft (cottage industry) to the putting-out system (manufacture) was taking shape during the late Edo period, Japan was still far from establishing a modern capitalist economy or an industrial revolution. 

Though this Edo-period system lacked automated machinery and factory-based mass production, it cultivated an exceptionally sophisticated network of specialized manual skills. When the Meiji Restoration(1868), it was precisely this deep-rooted tradition of pre-industrial craftsmanship that provided the fertile ground for Japan to absorb Western science and swiftly accomplish its state-led Industrial Revolution. 

The End of Japanese Seasonal Time System & Wadokei

Following the Meiji Restoration, the new government abruptly issued an Dajokan Fukoku (Decree of the Grand Council of State) No. 337 on November 9, 1872. This decree shifted Japan’s calendar from the traditional lunisolar calendar to the solar calendar—specifically, the globally widely used Gregorian calendar.

The decree stated that the upcoming December 3 would instantly become January 1, 1873 and after that,  each day would be divided into 24 equal hours. With this sudden change, the traditional seasonal time system was abandoned, marking the end of the traditional Japanese temporal system and the era of wadokei. 

All of the artisans who made wadokei lost their livelihoods. 

However, some artisans continued to make them by modifying their mechanisms to adapt to Western time. Consequently, unique "modern" wadokei—crafted during the Meiji era and the early 1900s—still exist today. Furthermore, drawing upon the innate dexterity and exceptional aptitude for miniaturised, intricate craftsmanship deeply rooted in Japanese culture, many of these artisans transitioned to other precision industries, such as Western-style clockmaking, thereby laying the foundations for Japan's modern precision engineering.