How did South Koreans become younger?
South Korea changed its traditional age-counting system, making many citizens a year or two younger. In December 2022, a new law was passed, which came into effect last month. This changed the old way of calculating someone's age.
As per the old method, babies are considered one year old at birth. Then, on every 1st of January, a year is added to South Korean people's ages, regardless of their birthdate. This means that everyone (including newborn babies) becomes a year older on the 1st of January instead of on their birthdays. For example, a baby born on 31st December turns two the next day (pretty funny, right?).
There’s another method to calculate age. It's a mix of the international method and the old Korean age system. Under this method, a baby is born at zero years, and one year is added every 1st January. So, a person born in August 2003 would turn 20 this year according to the international system, 21 according to the mixed method, and 22 according to the old system.
Which method will be followed now?

Now, the international method will be used. Instead of getting older on the 1st of January, a person’s age will be based on their birthdate. This change makes everyone a year or two younger.
Some important things, like passports and retirement benefits, already use the international method to calculate one’s age. But for other things, like deciding on the school year or mandatory military duty, they still use the mixed counting technique.
So, what’s the reason behind this change?
Having three ways to calculate age is very confusing for people in South Korea. It has caused confusion in health recommendations, pensions, and social hierarchy. The majority of South Korean citizens support this change in the age-counting law.