Age → calculator

Exact age in years, months and days on today's date or any other, past or future — with the next birthday, the weekday you were born, and a clear rule for 29 February and the 31st of the month instead of a silent guess.

Result: years · months · days
Totals: months · weeks · days · hours
Leap day: birthday on 28 Feb

Step 1

Dates

Date of birth

Age at

Defaults to today. Pick a past date to see an age then, or a future one for an age to come.

Month-end rule. When a birthday or monthly anniversary does not exist in a month, it falls on that month's last day. Born on 29 February: your birthday is 28 February in common years. Born on 31 January: you are 1 month old on 28 or 29 February. Dates are calendar dates, so your time zone never shifts the result.

Step 2

Age

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Enter a date of birth to see the exact age.

No date of birth yet Pick a date of birth on the left. "Age at" defaults to today.

Age difference between two people

Person 1 — date of birth Person 2 — date of birth

Worth knowing

Months are not all the same length

"3 months and 2 days" depends on which months. The calculator counts whole calendar years, then whole calendar months, then the remaining days — the same way you would on a paper calendar — rather than dividing a day count by 30.44.

29 February birthdays

Here, a leap-day birthday is counted on 28 February in common years, so you turn a year older before March begins. Some laws use 1 March instead (the UK, for instance); for legal deadlines, check the rule that applies to you.

Totals are exact days

Total days is the real number of calendar days, leap days included. Hours are days × 24: the time of birth and daylight-saving changes are ignored, which is what an age means in everyday use.

The gap stays, the ratio moves

Two people are always the same number of days apart, but the ratio of their ages changes every year. A parent who is 3 times their child's age now will be 2 times that age later — and never the same ratio twice.

Nothing is uploaded

Your date of birth is used only in this browser tab. There is no account, no storage and no request to a server when you calculate.

Questions

How do I calculate my age on a specific date?

Enter your date of birth and change "Age at" to the date you need — an exam cut-off, a school admission date or a retirement date. The result is your completed age on that day.

Why is someone born on 31 January one month old on 28 February?

February has no 31st, so the monthly anniversary falls on its last day. Without that rule a 31st-of-the-month birthday would skip February entirely and the months would drift.

Can I work out an age in the future?

Yes. Set "Age at" to any future date to see how old someone will be then, or use the next birthday line to see when they turn a year older and on which weekday.

What does "days until next birthday" count?

Whole days from the "Age at" date to the next birthday. On the birthday itself it shows today, not a year away.

Other tools

Date Difference CalculatorDays between any two dates. Timestamp ConverterUnix time to a date and back. Percentage CalculatorQuick percentage maths. Monthly PlannerPlan the month ahead.