Two ways to count

The age you know, which goes up by one on your birthday, is called man-nenrei (満年齢, "full age"). It is the age used on official forms, at hospitals, at schools and in the law.

The older system is kazoedoshi (数え年, "counted age"). A baby is one year old at birth, and everyone gains a year on New Year's Day instead of on their birthday. A baby born on December 31 turns two the next day, on January 1.

Here is a person born on July 15, 1990, seen across two New Years.

Kazoedoshi is always one or two years higher. It is two years higher between New Year's Day and your birthday, and one year higher from your birthday to the end of the year. To work it out, subtract the birth year from the current year and add one. Your birthday does not matter.

What the law says

A law from 1902, known in Japanese as 年齢計算ニ関スル法律, says that age is counted from the day of birth, and it applies the Civil Code rule for counting periods. Under that rule, a person gains a year at the end of the day before their birthday. In daily life this makes no difference, and you can think of the age as going up on the birthday.

In 1949 Japan passed another law on the way of stating age (年齢のとなえ方に関する法律), which took effect on January 1, 1950. It asks the public to state age in the full-age way instead of kazoedoshi. It requires national and local government bodies to state age in the full-age way, and, if they have an unavoidable reason to use kazoedoshi, to say so clearly. That is why government forms, schools and hospitals all use the age you are used to.

Where kazoedoshi is still used

Kazoedoshi survives in traditions that go back centuries.

Yakudoshi (厄年, "unlucky years") are ages at which misfortune is believed to be more likely. They are counted in kazoedoshi. The main years given in common lists are 25, 42 and 61 for men, and 19, 33, 37 and 61 for women. The year before and the year after each of them are also treated with care. Age 42 for men and 33 for women are the most feared. Shrines and temples differ a little, so check with the one you plan to visit.

Longevity celebrations mark the ages of 60 (kanreki), 70 (koki), 77 (kiju), 80 (sanju), 88 (beiju) and so on. They were traditionally counted in kazoedoshi, and many families now use the full age. Kanreki is the one case where the choice makes no difference: a person is 61 in kazoedoshi and 60 in full age in the same year.

Shichi-Go-San (七五三, "seven-five-three") is the November festival for children aged 3, 5 and 7. It is traditionally counted in kazoedoshi too. Many families now go by the full age, or choose the year that suits the child and the family's schedule.

School years and the April 2 cut-off

The school year in Japan starts in April, and the cut-off for each year group is April 1. Children born between April 2 and the following April 1 are in the same grade. A child born on April 1 starts school a year before a child born on April 2, even though they are one day apart.

The reason is the age rule above. The School Education Act requires a child to start elementary school at the beginning of the first school year after the day the child reaches the age of six. A child born on April 1 reaches six at the end of March 31, so the school year that begins on April 1 is the right one. A child born on April 2 reaches six at the end of April 1, one day too late for that year, and starts a year later. Here is how children born in 2020 line up.

Children born from January 1 to April 1 are called hayaumare (早生まれ, "early born"). They are the youngest in their grade. Nurseries and kindergartens generally also set their classes by age on April 1.

Coming-of-age ceremonies follow the same year groups in many cities. In 2027, for example, the ceremony in many cities is for people born between April 2, 2006 and April 1, 2007.

What this means for forms

When a form asks for your age, give your full age unless it says otherwise. If someone asks how old you are while talking about a shrine visit or a celebration, they may mean kazoedoshi, so it is fine to ask which they mean. For school forms, the date that counts is April 1. The Japanese era converter helps with the dates on those forms.

Frequently asked questions

How do I work out my kazoedoshi?

Subtract your birth year from the current year and add one. Your birthday does not matter, so everyone born in the same year has the same kazoedoshi.

Are unlucky years counted by kazoedoshi or by my normal age?

Traditionally by kazoedoshi. Some shrines and temples also accept the full age, so ask when you book a purification ceremony.

What is the school-year cut-off in Japan?

April 1. Children born from April 2 to the following April 1 are in the same grade, and the school year runs from April 1 to March 31.

Sources

• Act on Calculation of Age, 1902 (年齢計算ニ関スル法律, in Japanese)
• Civil Code, Article 143: calculation of periods by the calendar (in Japanese)
• Act on the Way of Stating Age, 1949 (年齢のとなえ方に関する法律, in Japanese)
• School Education Act, Article 17: when children start school (in Japanese)
• Ordinance for Enforcement of the School Education Act, Article 59: the school year (in Japanese)
• The lists of unlucky years and the ages for celebrations are the commonly given ones. They differ by shrine, temple and family.

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Last updated: 2026-10-04