• Top
•  > Calendar History
•  > Calendar History 1

Calendar History 1

• The Source
• "Tai-in-taiyo-reki"
• Spread of the Guchu-reki and Kana-goyomi calendars

The Source

Japan's first calendar came from China via Korea. In the middle of the 6th century, the Yamato Imperial Court, which ruled Japan at the time, invited a priest from a country called Paekche (Kudara in Japanese), in what is now Korea, to learn from him how to draw up a calendar, as well as astronomy and geography. Reportedly, Japan organized its first calendar in the 12th year of Suiko (604).

Back then, all matters relating to the calendar were determined by the Imperial Court. Under the Ritsuryosei system of centralized administration under the Ritsuryo legal code of the Taika Reformation, the Onmyoryo of Nakatsukasasho was in charge of the task. An Onmyoryo was a government office that had jurisdiction over calendar preparation, astronomy, divination, etc. It was a time when calendars and divination were inseparable. From the end of 10th century, the task of preparing the calendar was handed down in the Kamo family, while astronomy passed through generations of the Abe family, its patriarch being Abe Seimei (921-1005), noted as an Onmyo-shi, or specialist in the realm of calendars and divination.

"Tai-in-taiyo-reki"

The calendar used then was called "Tai-in-taiyo-reki," a lunisolar calendar, or "Onmyo-reki."

Each month was adjusted to the cycle of moon's waxing and waning. Since the moon orbits the earth in about 29.5 days, adjustment was required and this was done by making months with either 30 days or 29 days, the former, "Dai-no-tsuki (long month)," the latter, "Sho-no-tsuki (short month)." Aside from the moon's orbit round the earth, the earth orbits the sun in 365.25 days, which, as we all know, causes the seasonal changes. Thus, merely repeating long and short months gradually produced a discrepancy between the actual season and the calendar. To compensate for this, a month called "Uru-zuki," or intercalary month, was inserted every few years to produce a year with 13 months, with the order of longer and shorter months changing year by year.

Unlike our contemporary calendar in which there is no change in the order of months, back then the fixing of a calendar was deemed so important that it was placed under the control of the imperial court and, in the later Edo period, under the superimposed military shogunate regime.

Spread of the Guchu-reki and Kana-goyomi calendars

The calendar established by Onmyo-ryo was called "Guchu-reki," one in which various words indicating seasons, annual events and daily good omens were written in Chinese characters and called "Reki-chu (calendar notes)." The Guchu-reki derives its name from the fact that the notes were written in detail.

This Guchu-reki, which was in service until the Edo period, was used particularly by noblemen in ancient and medieval times, individuals based their everyday activities on the calendar. They often wrote a personal diary in the blank spaces or on the back of their personal calendar. These entries remain left valuable historical records of the era.

With the spread of kana, Japan's phonetic alphabet, "Kana-goyomi," a simplified edition of Guchu-reki written in kana, appeared. In the middle of the 14th century calendars started to be printed and soon reached a broader range of users.

• Introduction
• Calendar History 2

• 
• 
  • 
  • 
• 

• 
• 

• Online Gallery

Copyright © 2016- National Diet Library, Japan. All Rights Reserved.