Age Calculator

The Age Calculator turns a date of birth into an exact chronological age: how many years, months, and days have passed between that date and today, or between that date and any other date you choose. It also reports cumulative totals - total months, weeks, days, hours, and minutes lived - the weekday you were born on, and how many days remain until your next birthday.

Age arithmetic looks trivial until you try to do it properly. Months have different lengths, leap years insert an extra day roughly every four years, and there is no single answer to "how many days is one month". This calculator borrows days from the actual length of the month preceding the target date rather than assuming a 30-day or 30.44-day average, so the years/months/days breakdown matches the way a calendar actually works and the way registrars, HR systems, and courts count age.

Everything runs in your browser. No date of birth is uploaded, logged, or stored anywhere, which matters because a date of birth is a piece of personal data that identity-theft checks routinely ask for. Once the page has loaded, the tool keeps working with no network connection, and results appear instantly as you change either date.

Age is counted the way people count it, by whole years elapsed, so a birthday later this year has not happened yet and does not count. That makes February the interesting month. Someone born on 29 February has a birthday on a date that exists once every four years, and the common convention, used here, is that they age on 1 March in non-leap years. Month arithmetic carries the same ambiguity as any date difference: the months are counted whole first and the leftover days after, which is why the day figure can look small next to the month figure. Totals in hours and minutes are computed from absolute elapsed time, so they account for the leap days in between rather than assuming 365-day years.