Time Commemoration Day

What Is Time Commemoration Day?

Every June 10th is "Time Commemoration Day" (時の記念日, Toki no Kinenbi) in Japan. It was established in 1920 by the Tokyo Astronomical Observatory (now the National Astronomical Observatory of Japan) and the Life Reform Alliance (生活改善同盟会) to encourage punctuality and a more rational way of life. The date comes from the Nihon Shoki (日本書紀), which records that on the 25th day of the 4th month of the 10th year of Emperor Tenji's reign (June 10, 671 in the Gregorian calendar), a water clock called a rōkoku (漏刻) was placed on a new platform and bells and drums were struck to announce the hours for the first time.

How the Day Came About

In 1920, a "Time" exhibition was held at the Tokyo Education Museum (the forerunner of the National Museum of Nature and Science). It was so popular that its run was extended, and it was during this exhibition that the organizers proposed creating Time Commemoration Day.

• Background: At the time, Japanese people were seen in Western countries as having a poor sense of time, and the day is said to have been meant to encourage interest in time and orderly, efficient habits.
• The Life Reform Alliance's goal: The alliance listed "keeping time accurately" as the first of its goals for improving daily life.
• Not a national holiday: Since June has no national holidays, some have called for making Time Commemoration Day one, but this has not happened.

The Rōkoku: The Beginning of Clocks in Japan

A rōkoku is a water clock that measures time using water flowing at a steady rate. The Nihon Shoki states that this water clock was made by Emperor Tenji himself when he was crown prince (Prince Naka no Ōe), and an entry for the 6th year of Empress Saimei's reign (660) also mentions a water clock being made. Every June 10th, Ōmi Jingū Shrine in Ōtsu, Shiga Prefecture, which enshrines Emperor Tenji, holds a "Rōkoku Festival."

Fun Facts About Time

• From variable to fixed hours: In the Edo period, Japan used a variable-hour system that divided daytime and nighttime separately based on sunrise and sunset. When Japan adopted the solar calendar in 1873, it switched to a fixed system dividing the day into 24 equal hours.
• Defining the second: The second was once defined by Earth's rotation, but it is now defined by the frequency of radiation emitted by cesium atoms.
• Leap seconds on the way out: Leap seconds, inserted to keep clocks in step with Earth's rotation, are set to be discontinued by 2035 under a 2022 decision of the General Conference on Weights and Measures.
• Janet's law: The idea explaining why time seems to pass faster as we age is attributed to the 19th-century French philosopher Paul Janet.

Ideas for Time Commemoration Day

• Check that the clocks at home and at work show the correct time.
• Write down how you spend a typical day and look for ways to improve it.
• Look into Ōmi Jingū's Rōkoku Festival or clock museums around Japan.
• Make a point of starting meetings and appointments right on time.

Announcing the Time for More Than 1,300 Years

Time Commemoration Day on June 10th recalls the water clock whose bells announced the hours more than 1,300 years ago. Today we can check the time instantly on a smartphone, but being able to share accurate time is still a foundation of how society works. Why not take a moment today to look again at the clocks around you and how you use your time?