Age Calculator — Exact Years, Months & Days

Introduction

The age calculator finds exact years, months, and days from a birth date to today — or any as-of date you pick. It also shows next birthday, weekday born, ISO week, decimal years, and common milestone dates. Leap days and month lengths stay on this device.

Formula

Age is the calendar difference between today and the birth date, expressed in years, months, and days (leap years included).

• today — Current local calendar date
• birth date — Date of birth

Step-by-step

1. Pick the date of birth.
2. Optionally change the as-of date (defaults to today).
3. Read years, months, days, next birthday, and milestone table.

Worked example

Someone born on 1 January 2000 is a whole number of years old on each 1 January thereafter, with extra months and days accumulating between birthdays. 29 February births use 28 February on non-leap years for the next birthday.

Use cases

• Find exact age for forms and applications
• Calculate days and hours lived
• See when 18th, 21st, or retirement-age birthdays fall
• Verify age eligibility cutoffs against a specific date

Frequently asked questions