Can it tell me the school entry year?

Not directly, but set the reference date to 1 April of the year in question and read the full age. A Japanese child enters the school year beginning on the first 1 April after the day following their sixth birthday, so being six on 1 April means starting that April.

What is the zodiac sign based on?

The Gregorian year. Some traditions start the zodiac year at the lunar new year or at setsubun instead, so people born in January or early February are sometimes assigned the previous year's sign. The tool decides mechanically by calendar year, so for births in that window check the previous sign as well.

Does it match how age is counted outside Japan?

Full age is counted the same way in most countries, so it transfers directly. The one difference is that Japanese law turns the age over the day before the birthday, where some countries use the birthday itself. The discrepancy lasts exactly one day, but if a requirement falls on that day, follow the rule of whoever is asking.

What if the reference date is before the birth date?

The person would not have been born yet, so the calculation stops and says so. Negative ages are never displayed.

Is the date of birth stored?

No, and nothing is sent. Everything happens in the page and is gone when the tab closes.

Why someone born on 1 April is in the earlier school year

Under the Act on Calculation of Age, age turns over at the end of the day before the birthday. Someone born on 1 April therefore reaches six at the end of 31 March, which puts them on the same side of the School Education Act's cutoff as a child born on 31 March. The tool counts the same way, so with 1 April as the reference date, births on 1 and 2 April differ by a year.

Birthdays on 29 February

Legally the age turns over at the end of 28 February, so in a common year it increases on the 28th, and that is what the tool does. In practice some registries treat 1 March as the day instead, and both conventions are in use. If an age requirement falls across the end of February, check which one the receiving office applies.

When does kazoe age increase?

You are one at birth and gain a year every New Year's Day; birthdays play no part. Someone born on 31 December turns two the next day. The gap from full age is two years before the birthday and one after. Some regions count yakudoshi and kanreki in kazoe and others in full years, so check local custom when working out the year of an observance.

How are months counted?

As calendar months. From 1 April 1990 to 5 September 2026 is 36 years, 5 months and 4 days, which is counted as 437 months. It is not an approximation from a day count, so births at the end of a month do not drift. The intended use is checking an infant's age in months.

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Age Calculator

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Enter a date of birth to get the exact age in years and months as of today or any date, the traditional Japanese count (kazoedoshi), days lived and days until the next birthday.

Input

Date of birth

As of

Leave empty for today. Set a date to know the age on that day (school entry, 1 April, etc.).

Output

Enter a date of birth and the age, traditional count and days lived appear here.

Japanese law turns the age over at the end of the day before the birthday, which is why someone born on 1 April belongs to the earlier school year. The tool counts the same way.

Or type what you want to work out

All tools

Why this one

Any reference date: Not only "how old today". School entry, exam eligibility, insurance conditions — age requirements are almost always written as "age on such-and-such a date", and today's age does not answer them. Leave the field blank for today, or enter a date to count again as of that day.
Both Western and kazoe age: Full age counts from zero at birth and rises on each birthday. Kazoe-doshi starts at one at birth and rises on New Year's Day. Japanese observances such as shichi-go-san, yakudoshi and kanreki are often quoted in kazoe, and without a conversion to hand you end up looking it up again.
Days lived and the next birthday: Days, weeks and months since birth, plus the days remaining to the next birthday. Useful wherever years alone are not enough: an infant's age in months, counting back to an anniversary, checking length of service.

How to use

Enter the date of birth
Pick it from the calendar or type it. Dates back into the nineteenth century work.
Set the reference date
Blank means today. Fill it in only when you need the age as of a different day, such as 1 April.
Read the result
Full age, kazoe age, days lived, days to the next birthday, the weekday of birth and the zodiac sign. "Copy result" takes the lot.

How age is counted

Why someone born on 1 April is in the earlier school year: Under the Act on Calculation of Age, age turns over at the end of the day before the birthday. Someone born on 1 April therefore reaches six at the end of 31 March, which puts them on the same side of the School Education Act's cutoff as a child born on 31 March. The tool counts the same way, so with 1 April as the reference date, births on 1 and 2 April differ by a year.
Birthdays on 29 February: Legally the age turns over at the end of 28 February, so in a common year it increases on the 28th, and that is what the tool does. In practice some registries treat 1 March as the day instead, and both conventions are in use. If an age requirement falls across the end of February, check which one the receiving office applies.
When does kazoe age increase?: You are one at birth and gain a year every New Year's Day; birthdays play no part. Someone born on 31 December turns two the next day. The gap from full age is two years before the birthday and one after. Some regions count yakudoshi and kanreki in kazoe and others in full years, so check local custom when working out the year of an observance.
How are months counted?: As calendar months. From 1 April 1990 to 5 September 2026 is 36 years, 5 months and 4 days, which is counted as 437 months. It is not an approximation from a day count, so births at the end of a month do not drift. The intended use is checking an infant's age in months.

FAQ

Can it tell me the school entry year?: Not directly, but set the reference date to 1 April of the year in question and read the full age. A Japanese child enters the school year beginning on the first 1 April after the day following their sixth birthday, so being six on 1 April means starting that April.
What is the zodiac sign based on?: The Gregorian year. Some traditions start the zodiac year at the lunar new year or at setsubun instead, so people born in January or early February are sometimes assigned the previous year's sign. The tool decides mechanically by calendar year, so for births in that window check the previous sign as well.
Does it match how age is counted outside Japan?: Full age is counted the same way in most countries, so it transfers directly. The one difference is that Japanese law turns the age over the day before the birthday, where some countries use the birthday itself. The discrepancy lasts exactly one day, but if a requirement falls on that day, follow the rule of whoever is asking.
What if the reference date is before the birth date?: The person would not have been born yet, so the calculation stops and says so. Negative ages are never displayed.
Is the date of birth stored?: No, and nothing is sent. Everything happens in the page and is gone when the tab closes.

Input

Output

Related tools

Why this one

How to use

Enter the date of birth

Set the reference date

Read the result

How age is counted

FAQ