One birthday, several ages
Most of us assume age is universal: count the years since birth, done. But age is a cultural convention as much as a measurement. The two big questions every system must answer are: what age are you at birth? (zero or one?) and when does your age go up? (on your birthday, or on a fixed day for everyone?). Different answers produce systems that can disagree by up to two years.
The international (Western) system
You start at age 0 and gain a year on each anniversary of your birth date. This is the system used by almost every country for legal and official purposes, and the one used in our age calculator. The method behind it is explained in How Age is Calculated.
Korean age (μΈλλμ΄)
In the traditional Korean system, a baby is 1 year old at birth (counting time in the womb, by one explanation), and everyone gets a year older together on 1 January β not on their birthday. A baby born on 31 December turns 2 the very next day, while still being days old internationally.
In June 2023, South Korea officially standardised on the international age system for legal and administrative purposes, but Korean age remains widely used socially β it determines forms of address, drinking-age conversation, and social hierarchy. Try our Korean Age Calculator to see both of your ages.
East Asian age reckoning
Korean age is one branch of a much older system that originated in China and spread across East Asia:
The traditional "nominal age" starts at 1 at birth and increments at Lunar New Year rather than 1 January. It's still referenced in rural areas, for zodiac matters, and in traditional fortune-telling, though official life uses international age (ε¨ε²).
Japan used the same count-from-one system until it was legally abolished in favour of international age (man nenrei, ζΊεΉ΄ι½’) starting in 1902, reinforced by a 1950 law. Today kazoedoshi survives only in traditional ceremonies, such as certain shrine rites and memorial customs.
The traditional "midwife age" also starts at one and follows the lunar calendar. It's still commonly used for zodiac years and life-milestone customs alongside the official international age.
Side-by-side comparison
For someone born on 15 October 1995, here's their age on 6 July 2026 under each system:
| System | Age at birth | Increments on | Age today |
|---|---|---|---|
| International | 0 | Birthday (15 Oct) | 30 |
| Korean (traditional) | 1 | 1 January | 32 |
| Chinese xūsuì | 1 | Lunar New Year | 32 |
The gap between international and traditional East Asian age is always 1 or 2 years: 2 before your birthday each year, 1 after it.
Other age-related traditions
- Months, not years, for babies. Nearly everywhere, infant age is given in weeks or months ("14 months old") because a year is too coarse for early development.
- Milestone ages differ. Legal adulthood is 18 in most countries, but 20 in Japan was the rule until 2022 (now 18), 21 for some purposes in the US and Singapore, and 15β16 for others elsewhere.
- Zodiac years. In East Asia, your zodiac animal (rat, ox, tigerβ¦) repeats every 12 years and your ben ming nian (zodiac year) is considered significant. Find yours with the Zodiac Sign Calculator.
- Half-birthdays and name days. In parts of Europe and Latin America, a person's name day (their saint's day) is celebrated with as much or more enthusiasm than their birthday.
Frequently asked questions
What's your Korean age?
See your international and traditional Korean age side by side β instantly.
Open the Korean Age Calculator β