Dear reader,
Once you’ve spent some time in Korea, foreign friends almost always end up asking me this: “Wait, what’s Korean age? Why do you have a later birthday than me but claim to be older?” Today, let me answer that properly. This is a letter about how Korea counts age, or more precisely, about the fact that Korea used to have two different ages.
Korea used to have two ages
Until quite recently, every Korean person had two ages at once.
The first is se-neun-nai, often called “Korean age.” It was the most widely used method. You’re one year old the moment you’re born. The time spent in the womb already counts as your first year. And regardless of your actual birthday, everyone gains a year together on January 1st. So a baby born on December 31st is only a day old, but the very next day, January 1st, that baby turns two.
The second is man-nai, the international age. You’re zero at birth, and you gain a year on each actual birthday. It’s the same method most of the world uses.
The same person could have two different ages under these systems. For example, someone born on December 31st is still 0 by international age the very next day, but already 2 by Korean age. Depending on when your birthday falls, the gap between the two ages could be one year or two.
So the law changed
On June 28, 2023, Korea decided to clear up the confusion. Under a new law, every legal and administrative context now uses man-nai (international age) exclusively. ID cards, medical records, contracts, and government services are all based on international age. In the single day the law took effect, more than 50 million Koreans became one or two years younger on paper. It made headlines both inside and outside Korea at the time.
That said, the law change didn’t erase the concept of Korean age itself. It disappeared from official documents, but it’s still very much alive in everyday conversation.
So why do people still ask your age?
Here’s where it gets interesting. Legally, everything runs on international age now, but Koreans still want to know each other’s ages, especially when they’ve just met. It’s not rudeness. It comes from the fact that the Korean language itself is structurally tied to age.
Korean has both formal and casual speech, and there are specific terms like hyung, noona, oppa, and unnie used for people older than you. Without knowing someone’s age, it’s hard to decide how to speak to them or what to call them. So when Koreans start a new relationship, they tend to check each other’s age, sometimes subtly, sometimes directly. It’s less about establishing a hierarchy and more like a necessary step for starting a conversation in Korean.
And the age that comes up in these conversations is often still the familiar Korean age, not the legal international one. When someone says “I’m twenty-five,” whether that’s Korean age or international age is usually something you figure out from context. The law changed, but that old sense of being one year old at birth still lingers in Korean language and culture.
Here’s what travelers need to know
As a traveler, you don’t need to memorize any of this. Just remember two things.
First, don’t be thrown off if a Korean person asks your age. It’s not rude. It comes naturally from Korea’s system of formal and casual speech.
Second, don’t be surprised if a Korean person’s stated age is off by a year or two from what’s on their passport. They’re probably speaking in Korean age. No need to think, “wait, that doesn’t add up.”
Even Koreans got confused
Honestly, this system was a headache for Koreans too, for a long time. Before the law changed, a giant panda at a Seoul zoo once had its birthday, and there was genuinely half-joking confusion over whether it was turning four, five, or six. If people got confused, imagine the panda. There was good reason for the law to change after all.
So if someone in Korea asks your age during your stay, feel free to smile and answer: “Which age would you like to know?”
See you in the next letter.
From Seoul, whigoori
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