Age CalculatorYTScript

Age Calculator

Enter a date of birth to see exact age in years, months, and days — plus the next birthday.

Runs in your browser — dates never leave this device
Date of birth
Age at the date of
In non-leap years, count the birthday as
Birth time (optional)

Time only affects hours, minutes, and seconds — not whether a birthday has been reached.

Age will show up here Enter a date of birth. You can change the “age at” date if you want a day other than today.

How to use it

  1. 1

    Enter the date of birth. The “age at” date starts as today and can be changed.

  2. 2

    Read the exact age in years, months, and days. Totals and the next birthday update as you type.

  3. 3

    Open the other pages for baby age, a pet age estimate, or the number of days between two dates.

How this calculator counts age

Age is given in completed years, months, and days — the units people actually use — not as total days divided by 365. A month is complete when the same day of the next month is reached. So 28 February to 28 March is one month, and 28 February to 31 March is one month and three days, not two month-ends counted as two whole months.

If you were born on 29 February, a non-leap year has no such day. This page counts the birthday as 28 February by default, and you can switch it to 1 March. Both answers are shown for the same example in the questions below.

The count uses the Gregorian calendar and your local calendar dates. A daylight-saving change does not add or remove a year, a month, or a day. Everything runs on this device; dates are not sent to our servers.

Some traditions count a child as one year old at birth. This tool reports calendar age only and is not meant for official documents.

Other date tools

Chronological age calculatorAge on an assessment date, with Y;M;D copyBaby age calculatorWeeks, calendar months, and days after birthDog age calculatorA size-based estimate in human yearsCat age calculatorAn estimate in human years from a public chartDays between datesCount days, with or without the end dateAdd or subtract daysMove a date by years, months, weeks, or daysDay of the week calculatorWeekday, day of year, and ISO week

Questions

How is age counted?

In completed years, months, and days — not total days divided by 365. A month is complete on the same day of the next month: 28 February to 28 March is one month, and 28 February to 31 March is one month and three days.

Why might another calculator differ by a day?

Month-end dates can be counted in more than one reasonable way. This site uses the same “anniversary day” rule as above, rather than treating two month-ends as a whole month.

What if I was born on 29 February?

In a non-leap year the birthday is counted as 28 February by default, and you can switch it to 1 March. For the same example, born 29 February 2004 and measured on 28 February 2025 is 21 years on the default, or 20 years, 11 months, and 30 days if you use 1 March.

Are my dates uploaded?

No. The calculation runs in your browser. Dates you enter are not sent to our servers.

Do you use lunar age or 虚岁?

This version only calculates calendar (Western) age. Some traditions count a child as one year old at birth and add a year at the lunar new year. That is not an official or legal age, and this page does not calculate it.