Age calculator

Calculate exact age in years, months and days from a date of birth, plus total weeks, hours and the date of the next birthday.

How to Calculate age

1
Enter the date of birth
Type or pick a date of birth. The result appears immediately, before you touch anything else.
2
Optionally set a comparison date
By default age is calculated as of today. Change the comparison date to see age at any past or future point, such as a contract date or an exam.
3
Read the exact age and the next birthday
See the age in years, months and days, the same figure in weeks or hours, and the date and weekday of the next birthday.

How the calendar age is worked out

Years, months and days are calculated the way a calendar works, not by dividing a day count. Going from a day of birth to a later day borrows from the previous month whenever the day-of-month figure would go negative, exactly like subtracting 15 from 10 on paper. That is why someone born on the 15th of January is exactly 2 months old on the 15th of March, rather than a slightly odd-looking 59 days. The calculation matches how people actually describe age out loud.

Leap years and February 29th birthdays

Every date is normalized to UTC midnight before any subtraction happens, so a daylight-saving clock change never shifts a day count by an hour and quietly breaks a result near a transition. Someone born on February 29th gets a real birthday every four years; in the years between, this calculator follows the convention used by most record-keeping systems and treats February 28th as the birthday, rather than jumping to March 1st.

Your dates never leave this tab

There is no upload and no server round trip: both dates are read straight out of the two fields on this page and the whole calculation runs in JavaScript in your browser. Nothing is written to a server, and only the fact that a calculation happened reaches analytics, never the dates themselves.

Frequently asked questions

How is age calculated for someone born on February 29th?

In a leap year, their birthday falls on February 29th as usual. In every other year, this tool treats February 28th as the birthday, which is the convention most official calculators and record systems use, rather than moving the date to March 1st.

Does the calculation include today?

Yes. Age is measured up to and including the comparison date, which defaults to today. Someone born earlier today shows as 0 days old, not a negative number or an error.

Can I calculate age as of a date in the past or future?

Yes, change the comparison date field to any date on or after the date of birth. This is useful for working out age at the time of a contract, a school enrollment cutoff or an exam.

What is the difference between calendar age and total days?

Calendar age (years, months, days) matches how people describe their age out loud and accounts for how many days each month actually has. Total days is a straight count of every day that has passed, which is handy for statistics but does not split cleanly into calendar units.

Does my date of birth get sent to a server?

No. Both dates stay in this browser tab. The calculation is plain JavaScript arithmetic, and nothing about the dates is logged or transmitted anywhere.

Can I get a Unix timestamp for the date of birth?

This calculator focuses on the age breakdown itself. For a Unix timestamp, open the timestamp converter with the same date; the two tools are built to be used together.

Why is the age in hours only approximate?

Age in hours is derived from the total number of days, using midnight as the reference point unless you turn on the optional time-of-birth field. Turning that on adds the extra hours and minutes from the actual time of birth for a more precise figure.