South Koreans have become a year or two younger today as new laws that require using only the international method of counting age took effect, replacing the country's traditional method.
Key points:
- South Korea's traditional age counting method starts at one at birth and increments every year on January 1
- Another system used for conscription and legal drinking and smoking ages will remain for now
- Similar traditional counting methods are informally used in China, Japan and Vietnam
Under the age system most commonly used in South Koreans' everyday life, people are deemed to be a year old at birth and a year is added every January 1.
Since the early 1960s, the country has used the international norm of calculating from zero at birth and adding a year on every birthday for medical and legal documents. But many South Koreans continued to use the traditional method for everything else.
In December, South Korea passed laws to scrap the traditional method and fully adopt the international standard.
"We expect legal disputes, complaints and social confusion that have been caused over how to calculate ages will be greatly reduced," Minister of Government Legislation Lee Wan-kyu told a briefing on Monday.
According to a government survey conducted in September 2022, 86 per cent of South Koreans said they would use the international age in their everyday life when the new laws took effect.
Another age system exists for conscription, school entrance and calculating the legal age to drink alcohol and smoke: a person's age is calculated from zero at birth and a year is added on January 1. Officials said that method would remain for the time being.
"Something that is often not understood is that the two systems are counting different things," Professor Robert Hymes, who studies Chinese history at Columbia University, said.
According to Professor Hymes, the traditional East Asian counting method counts how many calendar years someone has been alive through, whereas the Western system counts years as a unit — how many whole years has someone been alive for, as of their most recent birthday?
Informal use of similar traditional age-counting methods exists in other East Asian countries such as China, Japan and Vietnam.
In China, age was traditionally calculated based on birth date, starting at one, and ticking up every Lunar New Year. Today, this method is mostly used in rural areas or by the elderly, or in specific contexts such as during fortune-telling.
One theory behind the usage of these traditional counting methods is that according to traditional Chinese beliefs, counting from conception, the baby will be one year old by the time it is birthed.
However, according to Professor Hymes, children start at one because "as of that moment you have been alive in one calendar year".
For the international system, "you are measuring the period of whole years you've lived", hence it starts at zero.
Japan officially adopted the international system in the 1950s, and North Korea did the same in the 1980s.
"A paradoxical result of this is that while we often think of the East Asian system as much less accurate than the Western one, in fact, considered in terms of what it's counting, it's more accurate: it tells the exact number of calendar years during any part of which you've been alive," Professor Hymes said, calling the Western system "often highly approximate" in contrast.
Story first published on ABC News Australia