Why are Koreans 1-2 years older?
Two rules make Korean age different from the system used in most other countries.
First, a baby is 1 the day it is born. The logic is simple: the nine months spent in the womb count. Second, everyone in Korea ages together on January 1st, not on their individual birthdays. So a child born on December 31st turns 2 the very next day, January 1st.
The result? Depending on when your birthday falls, your Korean age can be one or two years higher than your international age. A person born in late December gets the biggest gap. Someone born in early January barely notices.
만 나이 vs. 세는 나이: what changed in 2023?
Korea actually had three age systems running at the same time until recently. 만 나이 (man na-i) is international age, counted from 0. 세는 나이 (se-neun na-i) is the traditional Korean age described above. There was also 연 나이 (yeon na-i), a third system used in some legal contexts that started at 0 but still added a year every January 1st.
In June 2023, the Korean government made 만 나이 the only official standard for legal documents, contracts, and public services. The goal was to end confusion. Before the change, your age on your ID, your age at the doctor, and your age among friends could all be different numbers.
But here is the thing: in daily life, most Koreans still use 세는 나이. When someone asks "몇 살이에요?" (how old are you?) in a casual setting, they almost always mean Korean age. The law changed. The culture has not, at least not yet.
Honorifics K-pop fans should know
If you watch K-dramas or follow K-pop, you have heard these words. They all depend on age, which is exactly why Korean age matters so much socially.
A girl's older brother or older male friend. When Rosé calls someone oppa, she means he was born before her.
A guy's older brother or older male friend. Jungkook calls Jin "hyung" because Jin is 5 years older.
Lisa calls Jisoo "unni" since Jisoo was born in 1995 and Lisa in 1997.
A guy's older sister or older female friend. You hear this a lot in K-dramas when a younger guy likes an older woman.
Same age. When two people are 동갑, they can drop the formalities and speak casually. Jimin and V are 동갑 (both born 1995), which is partly why they are so close.
The wrong honorific is a real social mistake in Korea, not just a grammar error. Getting someone's age right is how you know which word to use. That is the whole reason Korean age still matters, even after the 2023 law change.