Calculators & Time
Age counted by the calendar
Enter a date of birth for an exact age in years, months and days — counted the way a calendar counts, not by dividing milliseconds.
Choose a date of birth.
Counted by the calendar rather than by dividing milliseconds, so months of different lengths come out right — 31 January to 1 March is one month and one day.
- Runs in your browser
- No account required
- Free to use
How it works
Not a subtraction
Dividing the difference in milliseconds by the length of a year gives an answer that drifts, because years and months are not a fixed length. The calendar answer needs the actual month boundaries, which is why 31 January to 1 March is one month and one day rather than 30 days.
Month arithmetic clamps
31 January plus one month is 28 or 29 February, because 31 February does not exist. Every calendar does this, and getting it wrong is how an age calculator ends up a day out for anyone born at the end of a long month.
Compared at midnight
Dates are compared at local midnight, so the time of day cannot make someone a day younger than they are.
What it does
Exact and total figures
Years, months and days, plus the totals in months, weeks and days.
The next birthday
How many days away, and today when it is today.
Age at any date
Leave the second field blank for today, or set it to work out an age on a particular date — useful for eligibility cut-offs.
Runs in your browser
No account and no upload — what you type is never sent anywhere. Analytics records that the tool was opened, never what you put into it.
Practical advice
Getting a better result
- Set the second date to work out how old someone will be at a future event, or was at a past one.
- A 29 February birthday has no anniversary in most years; the next-birthday figure rolls to 1 March, which is what most jurisdictions do.
- The day of the week you were born is shown too, calculated from the date rather than looked up.
Questions
Things people ask
Why is the number of days different from what I calculated?
Almost certainly because of how months are counted. The years-months-days figure walks the calendar, so the days component is the remainder after whole months — not a straight division. The total days figure is the simple count, and both are shown.
How is a leap-year birthday handled?
29 February exists only every four years, so in other years the next birthday is reported as 1 March. That matches how most legal systems treat it, though conventions differ.
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