How does the age calculation work?

The calculator subtracts the birth date from the reference date, handling month and day boundaries correctly. It counts full years, then remaining months, then remaining days — the same way you would count on a calendar.

What is the reference date?

The reference date is the date you want to measure age against. It defaults to today but you can change it to any date — past or future — to calculate age at a specific point in time.

How is "next birthday" calculated?

The calculator finds the next occurrence of your birth month and day after the reference date and shows both the date and the number of days remaining.

Does it account for leap years?

Yes. The total days calculation uses actual calendar dates, so leap years (with 366 days) are handled automatically. February 29 birthdays will show March 1 as the next birthday in non-leap years.

Can I calculate age for a future date?

Yes. Set the reference date to a future date and the calculator will show the projected age at that point. This is useful for planning milestones or retirement dates.

DATDate & Time

Age Calculator

Calculate your exact age in years, months, and days. See total days lived, total weeks, and how many days until your next birthday.

Date of birth

Reference date(optional)

Try an example

Enter values above to see results

How It Works

Formula

\text{totalDays} = \frac{\Delta t}{86400000}

Where

$\Delta t$: Milliseconds between the birth date and the reference date
$\text{totalDays}$: Whole calendar days between the two dates
$86400000$: Milliseconds in one day (24 × 60 × 60 × 1000)

Enter your date of birth and an optional reference date (defaults to today). The calculator computes your exact age broken down into years, months, and days, plus total days and weeks lived and the date of your next birthday.

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