Age Calculator (Age, Chinese Zodiac, Hayaumare)
＋More features: age on any reference date, next birthday, milestone ages
Age on a reference date you choose
Calculates your age on a specific date — for example, the day you joined a company (the birth date selected above is used).
Next birthday and days since birth
Based on the birth date selected above, this shows the days until your next birthday and the total days since you were born.
Dates when you reach milestone ages
A list of the dates when you reach milestone ages in Japan, such as adulthood (18), kanreki (60) and beiju (88).
Just enter your birth date to instantly see how old you are today (or were on any date you choose). It also shows your Chinese zodiac animal and whether you are “hayaumare” — born between January 1 and April 1, which places you in the earlier school year in Japan. Handy when writing your age on a Japanese resume or application form, or checking how old you were on a given date.
How to use
- Pick your birth date in the three boxes above (today’s date is preselected).
- The moment you pick it, your age, Chinese zodiac animal and hayaumare status appear. No button needed.
- For “how old was I on my start date?” or the days until your next birthday, open “＋More features”.
How it is calculated
- Age: if the reference date is on or after the birthday (month and day), age = reference year − birth year; if it is before the birthday, subtract 1.
- Hayaumare (early-born): born January 1 – April 1. Japanese school years group children born April 2 to April 1 of the following year, so early-born children are the youngest in their school year and join the year above children born later in the same calendar year. April 1 birthdays count as hayaumare because, under Japanese law, you legally get older at the end of the day before your birthday (March 31).
- Chinese zodiac (the 12 animals): derived from the Western birth year on the 12-year cycle Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog and Boar (in Japan the twelfth sign 亥 is the boar).
- Born on February 29: in common years the year is added on March 1.
Sources (primary information)
- Act on the Calculation of Age (Act No. 50 of 1902) — how legal age is counted, in Japanese
https://laws.e-gov.go.jp/law/135AC1000000050 (accessed July 18, 2026) - School Education Act (Act No. 26 of 1947), Article 17 — the basis of the school-year cutoff, in Japanese
https://laws.e-gov.go.jp/law/322AC0000000026 (accessed July 18, 2026)
Assumptions and notes
- If you need the legally exact age for a contract or an administrative procedure in Japan, check it under the legal rule that age increases on the day before the birthday.
- The zodiac animal is assigned per calendar year (switching on January 1 of the Western year). Traditions that switch at Lunar New Year or setsubun may give a different animal for people born early in the year.
Frequently asked questions
Is this different from “kazoedoshi”?
Yes. Kazoedoshi is the traditional East Asian count in which you are 1 at birth and gain a year every New Year. This tool uses the standard modern count (age reached on the birthday), which is what Japanese forms normally ask for.
Why do April 1 birthdays go into the earlier school year?
Under Japanese law, age is added at the end of the day before the birthday, so a person born on April 1 turns a year older on March 31. Since school years are grouped by the age held as of April 1, they fall into the earlier year.
Which date should my age refer to on a resume?
Normally the age as of the submission date. Set the reference date in “＋More features” to the submission date to get that age.