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Age Calculator

Calculate age between two dates.

How to use this tool

Steps for using the Age Calculator.

  1. Enter the Date of birth: choose the month and day, then type the year (numbers only) — or click the calendar button to pick the date.
  2. Leave Age at date empty to use today, or set any past or future date. Press Calculate Age — or try one of the Quick examples.
  3. The result shows the exact age in years, months and days, plus totals in weeks, days, hours, minutes and seconds. Pick new dates on the two calendars and the result updates immediately.
  4. Below it, see the Next birthday countdown with the next five birthdays, Fun facts and Milestones such as 10,000 days old. Copy puts a text summary on the clipboard; New calculation goes back to the start.

Example

Age on a specific date

Dates
Date of birth: 1990-05-15
Age on: 2026-10-10
Result
36 years, 4 months, 25 days
13,297 days · 1,899 weeks 4 days · 436 months
Next birthday: Saturday 15 May 2027, turning 37, in 217 days

Common use cases

  • Finding someone's exact age on a given date for a form, contract or eligibility check.
  • Counting down the days to a birthday and seeing which weekday it falls on.
  • Celebrating milestones such as 10,000 days or 1 billion seconds old.
  • Checking expected values when writing or testing date-handling code.

How the exact age is calculated

An age is counted the way people say it: first the whole years since the most recent birthday, then the whole months since that birthday, then the remaining days. This is different from dividing the number of days by 365.25 — an average year length gives fractional ages that drift by a day or two around birthdays, while counting calendar months always lands exactly on the birthday.

Months have 28 to 31 days, so stepping month by month needs a rule for dates that don't exist in every month. If you were born on the 31st, a month later is the last day of a shorter month (for example 30 April or 28/29 February). People born on 29 February have their birthday counted on 28 February in common years — the convention used by most software; some jurisdictions use 1 March for legal purposes, so check if it matters.

Totals are exact counts of calendar days between the two dates. Weeks are whole weeks plus the leftover days, and hours and minutes are the days multiplied out — the calculator works with dates, not clock times, so it doesn't know the hour you were born. Because only calendar dates are used, time zones and daylight-saving changes can never move a result by a day, which is a classic source of off-by-one bugs in date code.

The Western zodiac sign uses the commonly published cut-off dates, which can shift by a day in some years. The Chinese zodiac animal is based on the Gregorian birth year; strictly it changes at the lunar new year in late January or February, so people born early in the year may belong to the previous animal.

Limitations

  • Works with calendar dates only — the time of birth and time zone are not taken into account.
  • Leap-day birthdays are counted on 28 February in common years; some legal systems use 1 March instead.
  • The Chinese zodiac uses the Gregorian year, not the lunar new year boundary.
  • Dates use the proleptic Gregorian calendar and are limited to ages up to 150 years.

Frequently asked questions

Why does my age in days not match years × 365?

Because of leap years. Every four years (with century exceptions) adds a 29 February, so the exact number of days is slightly more than years × 365.

Can I calculate an age on a past or future date?

Yes. Set the Age at date to any date after the date of birth — for example to check how old someone was on a specific day or will be at a future event.

Is my date of birth saved or sent anywhere?

No. The calculation runs in your browser and nothing you enter is stored or sent to a server or analytics.