About this tool
An age is easy to say and slightly annoying to work out, because months are not the same length. Counting backwards from 6 March to 30 November in your head takes a minute and usually produces two different answers on two attempts. This does the same arithmetic the same way every time: whole years first, then the whole months left over, then the days left over after that.
The awkward cases are the ones worth knowing about. A birthday on the 31st has no anniversary in a thirty-day month, so the tool uses the 30th. A birthday on 29 February has no anniversary in three years out of four, so it uses 28 February. Both dates are also treated as plain calendar dates rather than points in time, which means the result does not shift by a day when somebody opens the page on a phone that thinks it is in a different timezone.
Alongside the years-months-days line you get the total day count, which is the number people usually want when they are filling in something that asks for duration rather than age. Nothing is uploaded and nothing is stored: the calculation happens in the page you already have open, and the date of birth you typed disappears when you close it.
How to use this tool
- Enter the date of birth. Type it or pick it from the calendar. Any date works, including 29 February.
- Set the “Age as of” date. It starts on today's date. Change it if you need the age on some other day — a cutoff on a form, or a date in the past.
- Read the result. You get years, months and days, and underneath it the plain total: how many days have passed between the two dates.
What this tool does not do
- It does not know any age rule, cutoff or eligibility criterion. It tells you the age; checking that against your form's own instructions is up to you.
- It works with whole calendar dates, not times of day, so it cannot give an age in hours or minutes.
- It reads Gregorian dates only. A Vikram Samvat, Hijri or Tamil calendar date has to be converted first.
- It does not save the date you type. Reload the page and it is gone.
Common questions
Will the answer change if my phone's clock is set to another country?
No. Both dates are handled as calendar dates in UTC, not as moments in local time. That is deliberate — a birthday worked out in local time can land a day earlier or later depending on where the device thinks it is, and one day is exactly the sort of error that gets a form rejected.
I was born on the 31st. Why does it turn over on the 30th in some months?
There is no 31st in April, June, September or November, so the anniversary is clamped to the last day that exists — the 30th. Without that clamp the month would roll over into the 1st of the next one and every count after it would be off.
Does a 29 February birthday work?
Yes. In a leap year the anniversary falls on 29 February. In an ordinary year the same clamp applies and it falls on 28 February, so the age turns over at the end of the month rather than on 1 March.
What is the difference between the two lines of the result?
The first is calendar arithmetic: full years, then leftover full months, then leftover days. The second is a straight count of days, which ignores how long each month happened to be. Both describe the same gap.
Can I use a future date?
Yes. The “age as of” date can be any date on or after the date of birth. It only refuses when the second date comes before the first, because that is not an age.