Time & Date

Age Calculator

Enter a date of birth and the calculator works out the exact age on any date you choose — calendar-accurate, with leap years and month lengths handled properly.

Your date of birth stays in your browser. Nothing is uploaded.

How age is actually calculated

Age is a calendar measurement, not an arithmetic one. The right way to do it is to count whole years first, then whole months from that anniversary, then the leftover days — which is exactly what this calculator does.

The shortcut you will find on a lot of sites — total days ÷ 365 — is wrong roughly a quarter of the time, because it ignores leap days. Over 40 years it drifts by about ten days. It also produces nonsense like "39.997 years old".

Formulayears → then remaining whole months → then remaining days

Because months have different lengths, the leftover days depend on which month you land in. Someone born on 15 March is, on 14 March 36 years later, 35 years 11 months and 27 days old — 27 rather than 30 because the month being counted through is February.

What each number means

Years, months, days — the everyday answer, and the one used on forms and legal documents.
Total months — whole months only. The day of the month has to have been reached for the month to count.
Total weeks — full weeks, with the leftover days shown separately. Useful for babies and for pregnancy tracking.
Total days — the exact day count, leap days included. This is the figure to use for anything that has to be precise.
Total hours — days × 24. It ignores daylight-saving shifts, which cancel out over a year anyway.
Next birthday — the date, the weekday, and how many days away it is.

Leap years, and the 29 February problem

A leap year is any year divisible by 4, except century years that are not divisible by 400. So 2024 was a leap year, 2000 was, and 1900 was not. Calculators that skip that last rule get every date before 1900 wrong.

People born on 29 February — "leaplings" — only get a true birthday every four years. This calculator observes the birthday on 28 February in common years, which is the most widely used civil convention and the one most jurisdictions follow for coming of age. In a leap year, the real date is used.

If you need the legal answer for a specific country, check it: a few jurisdictions treat 1 March as the observed birthday instead. The underlying age in years is identical either way.

Worked examples

Born 1 January 2000, age on 1 January 2001?

Exactly 1 year — and 366 days, because 2000 was a leap year. A 365-day assumption would have said the birthday had already passed.

Born 29 February 2000, how old on 1 January 2026?

25 years, 10 months and 3 days. The next birthday falls on 28 February 2026, because 2026 is not a leap year.

How many days old is a baby born 15 June 2026 on 8 September 2026?

85 days — 12 full weeks and 1 day, or 2 months and 24 days.

Common uses

Forms and applications that ask for an exact age on a specific date.
Eligibility checks — pensions, school entry, insurance bands, licences.
Baby milestones in weeks and days during the first year.
Pets, where months matter far more than years.
Anniversaries and counting down to a birthday.

For the plain gap between two dates without the age framing, use the date calculator.

Frequently asked questions

How is age calculated exactly?

By counting whole calendar years from the date of birth, then whole months from that anniversary, then the remaining days. Months are counted as real calendar months, so the leftover days depend on the length of the month you are counting through.

Why is my age in days not just my age in years times 365?

Because roughly one year in four has 366 days. Over 40 years that adds about 10 extra days. Anything that has to be exact — legal deadlines, medical records, milestone counts — needs the real day count, which is what this calculator gives you.

How does it handle a 29 February birthday?

In leap years the birthday falls on 29 February as normal. In common years the calculator observes it on 28 February, which is the most common civil convention. Your age in whole years is the same under either rule.

Can I find my age on a date in the past or the future?

Yes — change the second date to anything you like. It defaults to today, but you can set it to a future deadline or a past event to find your age at that moment.

Why does it say the birth date cannot be after the target date?

Because there is no such thing as a negative age, and quietly flipping the dates would hide a typo. Swap the two dates and the calculation works normally.

Does the hours figure account for daylight saving time?

No. It is total days × 24. Daylight-saving shifts add and remove an hour twice a year and cancel out, so the only case where it matters is a span of a few months that crosses exactly one changeover — and even then it is one hour in thousands.