# What is my exact chronological age?

Works out a chronological age in years, months, and days from a birth date, on today or any date, with the total days and the next birthday.

- Page: https://www.acalculator.org/days/chronological-age-calculator
- JSON spec: https://www.acalculator.org/days/chronological-age-calculator.json
- Version: df62e1cbe4da

## Default answer

Example with the default inputs (Date of birth February 2, 2002, Age on October 5, 2026) on the example date Monday, October 5, 2026: You: 24 years, 8 months, 3 days old on October 5, 2026.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| birth | Date of birth | The day the person was born. |
| on | Age on | The date to work out the age on. Today, unless you change it. |
| name | Name | A name to use in the answer, for example your child’s name. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| age | Age | Whole years, then whole months, then days from the date of birth to the age-on date. |
| who | Who | The name you entered, or “You”. |
| years | Age in years | Completed years (birthdays passed). |
| months | Total months | Completed months since birth. |
| weeks | Total weeks | The total days as whole weeks and days. |
| days | Total days | Days from the date of birth to the age-on date. |
| bornOn | Born on a | The weekday of the date of birth. |
| next | Next birthday | The first birthday after the age-on date. A February 29 birthday is February 28 in other years. |
| daysToNext | Days to next birthday | Days from the age-on date to the next birthday. |
| turns | Turns | The age in years on the next birthday. |

## Method

Count whole years from the date of birth while the birthday is on or before the age-on date, then whole months the same way, then the days left.

## Assumptions

- A month is counted when the same day of the month is reached; when that month is shorter, its last day counts (January 31 plus one month is February 28, or 29 in a leap year).
- A February 29 birthday falls on February 28 in common years.
- Total days count from the date of birth up to the age-on date, the birth day itself not included, so a baby is 1 day old the day after birth.
- Dates are calendar days with no time of day or time zone, so daylight-saving changes cannot add or lose a day.
- A date of birth after the age-on date gives no answer.

## Worked examples

1. birth = 1990-01-15, on = 2024-12-31 gives age = {"years":34,"months":11,"days":16}, years = 34, months = 419, days = 12,769, next = 2025-01-15, daysToNext = 15, turns = 35. Source: U.S. Naval Observatory, Leap Years: the Gregorian leap year rule. https://aa.usno.navy.mil/faq/leap_years.
2. birth = 2000-03-01, on = 2024-02-28 gives age = {"years":23,"months":11,"days":27}, days = 8,764, next = 2024-03-01, daysToNext = 2. Source: U.S. Naval Observatory, Leap Years: the Gregorian leap year rule. https://aa.usno.navy.mil/faq/leap_years.
3. birth = 2000-02-29, on = 2026-02-28 gives age = {"years":26,"months":0,"days":0}, days = 9,496, bornOn = Tuesday, next = 2027-02-28, daysToNext = 365, turns = 27. Source: U.S. Naval Observatory, Leap Years: the Gregorian leap year rule. https://aa.usno.navy.mil/faq/leap_years.
4. birth = 2002-02-02, on = 2026-09-27, name = Pat gives age = {"years":24,"months":7,"days":25}, who = Pat, weeks = {"weeks":1286,"days":1}, days = 9,003, bornOn = Saturday, next = 2027-02-02, daysToNext = 128. Source: U.S. Naval Observatory, Leap Years: the Gregorian leap year rule. https://aa.usno.navy.mil/faq/leap_years.

## FAQ

### How do I calculate my chronological age?

Use our calculator above to find your exact chronological age. Enter your birth date and the date you want to calculate your age as of. The result shows your age in years, months, and days. For example, if you were born on January 15, 1990 and want to know your age on December 31, 2024, you would be 34 years, 11 months, and 16 days old.

### How is chronological age calculated?

Our calculator uses precise date arithmetic to determine your exact chronological age between two dates. We count the whole years, then the whole months, then the days between your birth date and the end date, accounting for leap years and varying month lengths. For example, if you were born on February 29, 2000 (a leap year), your birthday falls on February 28 in other years.

### What is the difference between chronological age and other age types?

Chronological age is your actual age based on the time that has passed since your birth date. It's the most commonly used measure of age for legal, medical, and social purposes. Biological age refers to how old your body appears based on various health markers, which may differ from your chronological age. Mental age is a measure of cognitive development compared to typical development at different chronological ages.

### What can I use this calculator for?

This calculator is perfect for calculating your current age, finding your age on a specific date in the past or future, determining eligibility for age-restricted activities, planning for milestone birthdays, and calculating age for legal documents. To compare two people, use the age difference calculator.

### How accurate is this age calculator?

Our chronological age calculator accounts for leap years (including century rules), varying month lengths (28, 29, 30, or 31 days), and precise day counting. It counts whole calendar days with no time of day or time zone, so the answer is exact to the day. Some tests and forms set their own rule for rounding days or months; follow that rule where it applies.

### Can I calculate age for someone else?

Yes, you can calculate the age of anyone by entering their birth date and the date you want to know their age as of. This is useful for parents tracking their children's ages, HR departments calculating employee ages, or anyone needing to determine someone's age for legal or administrative purposes.

### What if I want to know my age on a future date?

You can enter any future date as the end date to see what your age will be on that date. For example, if you want to know your age on your next birthday, simply enter your birth date and the date of your upcoming birthday. This is useful for planning milestone celebrations or understanding age requirements for future events.

### How does the calculator handle leap years?

The calculator correctly handles leap years by accounting for the extra day (February 29) in leap years. For example, if you were born on March 1, 2000, and want to know your age on February 28, 2024, you would be 23 years, 11 months, and 27 days old. The calculator properly accounts for the fact that 2024 is a leap year.

## Sources

- U.S. Naval Observatory, Leap Years: the Gregorian leap year rule. https://aa.usno.navy.mil/faq/leap_years