Age Calculator

Age in years, months and days is calendar arithmetic, not a division problem. The calculator steps forward from your date of birth one whole year at a time for as long as the result is still in the past, then one whole month at a time, then counts what is left over in days. That is why the answer reads the way you would actually say it — thirty-four years, two months and nine days — instead of a decimal nobody uses.

Months are not the same length, so the final day count depends on which month it lands in. Stepping forward one month from 31 January reaches 28 February in a common year and 29 February in a leap year, since there is no 31 February to land on. The calculator clamps to the last day of the shorter month, which is the convention civil registries and most legal definitions of age go by, and it does the same going in reverse, so your age never jumps by a day between two dates right next to each other.

Total days lived is a plain count of every day from one date to the other, including every 29 February that fell in between. A year is a leap year when it divides by four — except centuries, except centuries that divide by four hundred: 2000 was a leap year, 1900 was not. The calculator applies that exact rule instead of an average year length, so the total is precise, not close, and the weeks figure is the same total divided by seven.

If you were born on 29 February, you have no birthday at all in a common year. This calculator treats 1 March as the day you turn a year older in those years, the more common civil convention, and it says which convention it used instead of leaving you to figure out the number on your own. The total days lived is the same either way, since it counts real days and not birthdays.

A date has no time zone until something gives it one. Both dates here are read as plain calendar dates and compared directly, so your age does not shift by a day just because you opened this on a flight or because a server happens to sit in another country. Both dates stay in your browser and go nowhere else; nothing about a date of birth is stored, logged or sent anywhere.

By default the second date is today, taken straight from your device clock, and you can set it to any other date instead. That is what you need when a form asks for an age as at a particular day — a school cut-off, an insurance term, a visa application, a season that has not started yet. The next birthday line works the other way: it names the date, the day it falls on, and how many days are left. If what you actually need is the gap between two dates that are not your birthday, the days between dates calculator does that, and the countdown timer counts down to a moment in days, hours, minutes and seconds.