Age Calculator
Instantly get age in years, Japanese counted age, zodiac, era name, school grade, and days to the next birthday from a birth date.
About this tool
The age calculator derives current age, counted age, zodiac, Japanese-era year, school grade, and days until the next birthday from a birth date. It runs in your browser and never sends the birth date anywhere. Age has a few uniquely Japanese rules worth understanding.
Current age and counted age
Current (ζΊ) age counts the birthdays reached and is the most common age today. Counted age (kazoedoshi) treats birth as age one and adds a year each New Year's Day β a traditional method used for celebrations like Shichi-Go-San and the 60th-birthday kanreki. The same person can have different ages by method.
Legally, you age on the day before your birthday
Under Japan's Act on Calculation of Age, a person is treated as gaining a year at the end of the day before their birthday. That is why someone born on April 1 is an "early birthday" and enters the higher school grade β they are treated as aging on March 31, the day before.
Early birthdays and school grade
A Japanese school grade groups those born from April 2 through April 1 of the next year. People born January 1 to April 1 are "early birthdays" and land one grade above others born later the same calendar year. The tool determines the grade by this rule.
Japanese-era and zodiac display
The Japanese-era (wareki) birth year and the zodiac are shown based on Japan's calendar and systems, which helps when a form asks for the wareki date.
How to use
- Enter a date of birth as YYYY-MM-DD to get the age as of today.
- Besides age in years, it shows Japanese counted age (kazoedoshi), zodiac sign, era name (wareki), school grade, days until the next birthday, and whether the person is early-born.
- Results update as you type and are computed entirely in your browser.
FAQ
Is the birth date I enter sent to a server?
No. All age calculation runs in your browser, so the birth date you enter never leaves your device.
How does current age differ from counted age?
Current age counts the number of birthdays reached and is the common everyday age. Counted age treats birth as age one and adds a year each New Year's Day β a traditional method used for milestone celebrations.
Is the grade for early-birthday children correct?
Yes. Japanese school grades are divided at April 2, so children born between January and April 1 ("early birthdays") fall into the higher grade. The tool applies this rule when showing the grade.
Does it show the Japanese-era (wareki) year?
Yes. You can see the birth year expressed with the Japanese era name, which helps when a form asks for the wareki date.
What is the days-until-next-birthday based on?
It shows the days remaining from the reference date (usually today) to the next upcoming birthday. Confirm whether the birthday itself should be included for your purpose.
Does it handle leap-year (February 29) birthdays?
Yes, it can calculate for those born on February 29. Note that which day counts as the birthday in common years can vary by rule or custom, so check the prescribed rules for official procedures.