How the calendar and the eto fit together

1.The eto year begins at Risshun

The ancient Chinese calendar treated the time from one winter solstice to the next as the solar year, and marked the seasons with the 24 solar terms that divide it. Today’s solar terms split the sun’s path into 15° steps, a method Japan adopted with the Tenpō calendar of 1844. Of these, Risshun is the start of spring, and was also seen as the start of a new year.

So in eto-based fortune-telling, anyone born before the moment of Risshun (up to Setsubun, the day before, and on Risshun itself before the exact time) takes the previous year’s eto. Someone born on 20 January 2026, for example, has the year eto 乙巳 (Kinoto-mi) from the year before, not 丙午.

2.Month eto change at the solar terms

Month eto do not change on the first of the calendar month either. They change at the setsu terms: Risshun, Keichitsu, Seimei, Rikka, Bōshu, Shōsho, Risshū, Hakuro, Kanro, Rittō, Taisetsu and Shōkan. These are the solar months (setsugetsu).

The stem of each month depends on the stem of the year. In a 甲 or 己 year, for example, the Tiger month begins as 丙寅.

3.Day eto have run unbroken for over 2,000 years

The day eto are untouched by leap months or calendar reforms; they simply keep turning every 60 days. Records show the cycle running without a break from at least the Spring and Autumn period (8th century BC) to today, and some think it goes back unbroken to the Shang dynasty.

4.How this differs from the lunar calendar

The old lunisolar calendar set its months by the phases of the moon and used leap months to stay in step with the seasons. Solar months, in contrast, follow the sun alone, so they always match the seasons. The eto months are solar months, not lunar ones.

You can check today’s eto and festival days in the eto calendar.