Age calculator — from birthday to years, zodiac & day count
Enter a birth date and a reference date to get the full age in years, days lived, Eastern zodiac (12 animals), and Western zodiac. Change the reference date to compute the age at any past or future point. Everything runs inside your browser — your birthday never leaves the page.
How to use
Enter a date of birth and a reference date (today by default) to instantly see the full age, a years/months/days breakdown, kazoe-doshi (East Asian count), days/months lived, the Eastern zodiac animal, the Western zodiac sign, and days until the next birthday. The reference date is editable, so you can ask 'how old will I be on 2027-04-01?' or 'how old was I at the wedding?'. The Today button resets the reference to today. Copy puts a summary on the clipboard.
FAQ
- Is the birth date uploaded?
- No. Everything is computed by JavaScript in your browser. Nothing is sent to any server, so it is safe to enter personal birthdays.
- What is kazoe-doshi (数え年)?
- A traditional East Asian way of counting age: you are 1 at birth and +1 every New Year's Day. This tool computes it as (reference year - birth year + 1). It is used for Japanese yakudoshi (unlucky years), mourning postcards, and traditional ceremonies.
- How is the Eastern zodiac chosen?
- By the birth year modulo 12 (using 1924 = Rat as anchor). We use the Gregorian Jan 1 boundary, so this can differ from systems that use the lunar calendar (where the year changes around Setsubun in early February).
- Why do the zodiac dates look slightly different?
- Western zodiac signs depend on the Sun's position on the ecliptic, which actually shifts by 1-2 days year to year. We use the commonly cited dates (e.g., Aries is Mar 21 - Apr 19).
- Can the reference date be in the future?
- Yes. Use it for 'how old will I be on my retirement date?' kinds of questions. If the birth date is later than the reference date, the tool shows an error.
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