Age calculator

Date of birthReference date (default: today)

Age

Pick a date of birth.

Rule: one year is added on the birthday. For a Feb 29 birthday in a common year, it is added on March 1 (Civil Act Art. 158, 160).

The dates you enter stay in this browser and are not uploaded.

Dates you enter never leave this device.

How to use it

1
Enter the birth date
Pick the year, month, and day of birth in the date box. The date is read in this browser tab only and is not uploaded.
2
Check the reference date
The reference date starts as today on your device. Change it to find an age on a past or future day, such as an application deadline.
3
Read the age
The age in completed years appears right away. If the reference date is before the birth date, you see an error message instead of a number.
4
Try another date
Edit either date to compare. Nothing is saved, so closing the tab clears the dates.

Common use cases

Eligibility checks

Check whether someone meets a minimum or maximum age on the day an application, enrollment, or contract starts.

Forms and paperwork

Fill in an age field on a form with the age counted the same way Korean public offices count it.

Leap day birthdays

See when a February 29 birthday adds a year in a common year. In this tool the year is added on March 1.

Security and privacy

Your dates stay on your device

The age is calculated by browser code on your device while you type. No upload route exists for this tool, no request carries your dates, and nothing is saved after you close the tab. You can enter a family member's birth date without sending it to anyone.

Supported inputs and outputs

What it uses

A birth date: year, month, and day
A reference date, set to today on your device by default
Age in completed years, counting the birth day itself
February 29 births: one year is added on March 1 in common years

FAQ

Are my dates uploaded?

No. The calculation runs inside your browser. No request that carries your dates is sent to Frisbly or anyone else.

How is the age counted?

It is the age in completed years. You become one year older on the day of your birthday. Korean civil law counts age this way (Civil Act Articles 158 and 160), and Korean administration uses it too (Framework Act on Administration Article 7-2).

What about a February 29 birthday?

In a leap year the birthday is February 29. In a common year the period ends on the last day of February, so one year is added on March 1. This is how the Civil Act rule on months without the matching day is applied here.

Why does the reference date matter?

Age changes every year on the birthday. A reference date lets you ask how old someone is, or will be, on any given day.

Can this replace an official record?

No. It is a convenience calculator. For legal or official use, check the rules of the office or law that applies to you.