Age Calculator

Guide: Age Calculator

How the age calculation works

Your age in years, months and days is a calendar difference, not a division of days by 365. Write both dates as year, month and day, then subtract each part. If the days come out negative, borrow the number of days in the month before the target date and reduce the months by one; if months go negative, borrow 12 months from the years.

Example

Born 15 January 2000, measured on 10 March 2024: years 24, months 2, days −5. Borrow February 2024 (29 days): 24 years, 1 month, 24 days. Dates are compared as pure calendar days in UTC, so daylight-saving changes never shift the result.

Days lived and the next birthday

• Days lived = the exact count of calendar days between the dates; leap days are included.
• Weeks lived = days ÷ 7, rounded down.
• Next birthday = the first date on or after today that has your birth month and day; the countdown is the day difference to it.
• Born on a shows the weekday of your birth date.

Good to know

People born on 29 February are counted on 28 February in common years here. Results use the date you enter and your device date as the default for "today", so a device with the wrong date will show a wrong age. The "Copy result" button stores a one-line summary you can paste anywhere.

FAQ

How is exact age calculated?

We subtract the birth date from the target date year by year, month by month and day by day. If the day difference is negative, we borrow the length of the previous month.

Can I calculate age on a past or future date?

Yes. Change the second date to any day, such as a job start date or an exam deadline, to see the age on that day.

What happens for a Feb 29 birthday?

In non-leap years this calculator counts the birthday on Feb 28. Some places legally use Mar 1 instead, so check local rules if it matters.

How many days have I lived?

It is the number of calendar days between your birth date and the chosen date. Weeks, months and hours shown are derived from it.

Is my birth date sent anywhere?

No. The calculation runs in your browser; nothing is submitted by this tool.