Who this helps
- People checking age on a specific date
- People comparing birthdays and age-counting conventions
Date Utility
Age Calculator
Enter a birth date to calculate full age, year age, Korean age, days lived, and days left until the next birthday.
Full Age Calculation
Calculate age based on whether the birthday has passed.
Korean Age Comparison
Compare year age and traditional Korean counting age together.
Birthday Information
Check the days left until the next birthday and the weekday.
Age Calculation Settings
Enter a birth date and base date to view age results by different standards.
Full Age
-Year Age
-Korean Age
-Until Next Birthday
-Details
- Birth Date: -
- Base Date: -
- Days Lived: -
- Next Birthday: -
Recent Calculation History
Reload recently calculated birth date results.
No saved calculation history yet.
Compare full age, year difference and Korean counting age
Enter a birth date and reference date to check completed years, the year difference and traditional Korean counting age. The page also shows calendar days since birth and the next birthday. These are distinct calculations, so choose the one your task calls for.
When to use this tool
- Compare results just before and on a birthday.
- Check days remaining until the next birthday.
From input to a checked result
- 1
Enter the birth date.
- 2
Select the reference date or use Today.
- 3
Read full age first, then compare the year-based figures.
- 4
Check the next birthday and days lived; use the relevant institution’s rules for eligibility.
Before this year’s birthday
- Input
- Birth: 2000-10-20 Reference: 2026-08-06
- Result
- Full age: 25 · Year difference: 26 · Korean counting age: 27
The birthday has not arrived, so full age is one less than the year difference.
On the birthday
- Input
- Birth: 2000-08-06 Reference: 2026-08-06
- Result
- Full age: 26 · Next birthday: today
The birthday is included when determining completed years.
How it works
Full age is the reference year minus the birth year, minus one if the month/day of the birthday is still ahead. Year age is the year difference alone; Korean counting age adds one to that difference and uses January 1 as the annual boundary. Days lived and days to the next birthday compare calendar dates without subtracting local daylight-saving offsets.
Limitations
- The calculation does not determine eligibility under a particular school, insurance or legal rule.
- For a February 29 birth, this tool uses March 1 in non-leap years for the next birthday and age transition.
- The counting-age figure is the Korean January 1 convention, not a lunar-calendar age system.
- Birth time and time of day are not included.
Your data
Calculations run in your browser; up to 10 recent birth/reference-date pairs are kept in localStorage. Clear history on a shared device. The share URL includes the birth date and reference date, which may be visible to recipients and in site access logs.
References
Related tools
- Date Difference Calculator
Compare calendar days or weekdays.
- D-Day Calculator
Save a countdown to a birthday.
Frequently asked questions
Why is full age smaller than the year difference?
Before the birthday, the current year of life has not been completed. Full age subtracts one until that month and day arrives.
How is a February 29 birthday treated?
In a non-leap year this tool shows March 1. On February 28 the birthday is still ahead. This describes the calculator’s convention, not a universal legal rule.
Are days lived a count of complete 24-hour periods?
No. They are the difference between calendar dates. Birth time and daylight-saving hour changes are not counted.