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ToolNestora

Age Calculator

Enter a date of birth and see the exact age in years, months and days, the total number of months, weeks, days and hours lived, the weekday you were born on and how many days remain until the next birthday. You can also measure the age on any other date, past or future. The calculation runs in your browser.

Calculate an age

Pick a date or type it as year-month-day.

Leave empty to use today's date.

Enter a date of birth to see the age.

How to use it

  1. Enter the date of birth

    Pick the date from the calendar or type it as year-month-day, for example 1990-04-27.

  2. Choose another date if you need one

    Leave “Age on this date” empty to use today. Fill it in to find an age on a specific day, such as the first day of school or a future deadline.

  3. Read the result

    The age appears as years, months and days, with the totals and the next birthday underneath.

Example: checking an age on a cut-off date

A club requires members to be at least 8 years old on 1 September 2026. Enter the child's date of birth and set “Age on this date” to 2026-09-01. If the result shows 8 years or more, the child qualifies. The tool measures whole calendar dates, so the time of birth does not matter.

How the age is counted

These are the rules the calculator follows, so you can check them against any official definition you need to meet.

Rules used for the age calculation
PartRule
Years and monthsWhole months are counted from the date of birth. When the day of the month does not exist (31 January plus one month), the last day of that month is used.
DaysThe days left over after the last whole month, up to the measured date.
Total days and weeksCalendar days between the two dates. Weeks are whole weeks of 7 days.
Total hoursWhole days multiplied by 24. Dates carry no time of day, so this is not an exact count of hours.
Next birthdayThe next date on or after the measured date with the same month and day. A 29 February birthday is shown on 28 February in years without one.

Limits and limitations

  • Only dates are used, not times or time zones. Someone born late in the evening and someone born early in the morning of the same day have the same age here.
  • Years from 1000 to 9999 are accepted. Calendar dates are counted with the modern Gregorian calendar, even for dates before it was adopted.
  • Different countries and institutions treat 29 February birthdays differently. This tool counts the birthday on 28 February in years without a 29th.
  • The result is for general use. For a legal or medical purpose, use the definition that applies to that purpose.

Frequently asked questions

Is my date of birth stored or sent anywhere?

No. The date you enter is processed by JavaScript running in your browser and is not sent to a server. The page itself still loads from a web server like any website. This site can load advertising or analytics scripts, but only after you accept them in the cookie notice. They are separate from the tools, which never pass the files or text you work with to them.

Why does the day count change when I choose a different end date?

The age is always the time between the date of birth and the date you are measuring to. Changing the second date changes the answer, and leaving it empty means today on your own device's calendar.

Is a person who turns 18 today already 18?

Yes. On the birthday itself the years go up by one and the months and days show 0.

How is the weekday of birth worked out?

From the calendar date alone, using the Gregorian calendar. It does not depend on your time zone.

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