Age Calculator — years, months and days

How it works

Age is how much calendar time has passed since you were born. This calculator peels it off in the usual order — whole years first, then whole months, then the leftover days:

age = as-of date − date of birth

The as-of date defaults to today, so you see your current age, but you can set it to any date — a past or future birthday, or the day of an event. Because the calculation counts real calendar time, it respects the different month lengths and leap years automatically: a year is a leap year (with a February 29) if divisible by 4, except centurial years, which must be divisible by 400.

Adding a month clamps to the shorter month where needed — one month after January 31 is February 28 (or 29 in a leap year) — which is how ages and monthly anniversaries are normally read. The total days lived is simply the whole number of days between the two dates.

Worked example

Someone born 2000-01-01 is 26 years, 0 months, 0 days old on 2026-01-01. The day before a 30th birthday — 1990-03-15 to 2020-03-14 — is 29 years, 11 months; one day later it is exactly 30 years. A leap-day baby born 2000-02-29 is 25 years, 10 months, 4 days on 2026-01-01.

Frequently asked questions

How do I calculate my exact age?

Subtract your date of birth from today's date, counting whole years, then whole months, then the remaining days: age = as-of date − date of birth. Someone born on 2000-01-01 is 26 years, 0 months, 0 days old on 2026-01-01.

How is age counted in years, months and days?

The calculator counts complete years first, then complete months, then the days left over — the way age is normally spoken. Adding a month clamps to the shorter month when needed, so one month after January 31 is the end of February.

How does it handle leap years and February 29?

Leap days are included in the day count, so total days lived and the months/days breakdown are exact. A leap-day birthday (February 29) is treated as reaching the end of February in common years, which is why the breakdown lands on February 28 outside leap years.

Does the age update to today automatically?

Yes — the as-of date defaults to today, so on page load it shows your current age. You can change the as-of date to any past or future date to see your age then, for example on an upcoming birthday.

How many days have I lived?

The total-days figure is the whole number of days between your birth date and the as-of date, counting every calendar day including leap days. It is the same count the days-between calculation gives.

Why is my age different by a day some years?

Because a common year is 365 days — 52 weeks and one day — while a leap year is 366. That extra day means the exact days in each year of your life vary slightly, though your age in whole years changes only on your birthday.