The Seasonal Time System of Historic Japan

There was an article at Japonica Publications about the time system used in Japan before the coming of the time system we are familiar with in the West. An except is below. The full post may be read here.

Isolated for centuries while the rest of the world was industrializing, Japan developed many unique ways of living. One of the strangest to our modern thinking was a system for counting time where the length of an hour changed daily.

The way of counting time used everywhere now is called a “fixed hour system.” Each day has 24 hours, and each hour is the same length of time. We further divide each hour into 60 minutes of 60 seconds, derived from Babylonian numerology.

A fixed time system is well suited to mechanical (and now electrical) time counting devices — clocks. A clock uses either a pendulum or spring (and now quartz crystals) to mark fixed amounts of time. Add the right set of gears (or chips) and it’s easy to count the minutes and hours of the day.

Since we’ve lived with a fixed time system all our lives, we assume this is the only way to divide time.

However, in an unmechanized, agrarian society, a set amount of time per hour isn’t the most obvious way to count time. For a farmer, daytime is the time between sunrise and sunset, night is the time when it’s dark.

It’s natural to divide daytime into a few separate periods: early morning, mid-morning, noon, early afternoon, mid-afternoon, sunset. And this is exactly how Japan’s time system worked.

What mattered was not some fixed amount of time, but where we were in the day. Of course, as the length of the day changed daily, the length of each period also expanded and contracted. But mid-morning was always 2/3 of the time from daybreak until noon.

This unfixed time system, called futeijihō (不定時法) in Japanese, is also called the “temporal hour system” or “seasonal time system.”

Japan’s unfixed time was used for hundreds of years during the Edo Period until the modernization of the Meiji Era. Here’s how it worked:

Japan’s Unfixed Time

Based on the Chinese horoscope, a day was divided into 12 segments, each called an ittoki (一刻, one toki).

(Note: while 一刻 is read now as ikkoku, it was ittoki then.)

Daytime — the time between sunrise and sunset — was divided into 6 toki. Nighttime — from sunset until dawn — was separately divided into 6 toki.

At the spring and autumnal equinox, the length of day and night is the same. But during the summer, the day is long, and in winter, the sun sets early and rises late.

Consequently, the length of each toki is different between day and night. It also depends on the day of the year and on the latitude, which varys widely across Japan.

Still, without mechanized timekeeping, this ittoki system was easy to understand. People only needed to divide the day evenly. Six toki during the day meant 3 toki from dawn until noon, then 3 more toki until sunset.

Confusingly though, instead of simply counting from 0–12, toki were counted down from 9 to 4, twice each day. The numbers 1–3 couldn’t be used because they referred to Buddhist prayer times. Toki were counted down instead of up because before clocks arrived, special incense sticks were used to count down the time as it burned.

The Chinese zodiac animals were also used to describe the hour. Midnight was ne no koku (子の刻 — hour of the rat). People believed ghosts would appear during ushi no koku (丑の刻 — hour of the ox), roughly 2 AM. To place a curse on someone, you visited a shrine at the time of ushi no koku and nailed a straw doll to a tree.

We still use the word oyatsu (お八つ) to refer to an afternoon snack. The word literally means 8, because 8 toki was early afternoon, roughly 2 PM.