Updated June 28, 2023 at 9:56 AM ET

SEOUL, South Korea — You're not getting any younger — unless you live in South Korea.

South Koreans all got one or two years younger on Wednesday, as a new law went into effect and the country dropped a traditional method of determining their ages.

Under the traditional system, sometimes known as "Korean age," a person is one year old at birth, and gains a year every New Year's Day. A baby born on Dec. 31 would be considered 2 years old the next day.

Government agencies have been using the international system for decades for most official business.

But seniority is very important in Korean society and workplaces, and the Korean age is still used in certain industries, such as matchmaking.

For things like the legal age for smoking, drinking, going to school or serving in the military, the government will consider citizens' year of birth, but not the date.

Most South Koreans support this change

More than 80% of South Koreans supported unifying the age-counting system, according to a poll by the Ministry of Government Legislation last September.

And 86% said they would go by their birth date age in their daily lives, according to the poll.

South Korean President Yoon Suk Yeol had promised to unify the country's age-counting systems on the campaign trail earlier last year, saying that they created "unnecessary social and economic costs."

South Korea has been tallying age by birth dates since the 1960s.

But while most East Asian countries have scrapped the traditional age-counting system, some have yet to follow suit.

For example, in China, which uses the nominal age-counting system, a person is considered 1 year old on the day they are born, and they gain a year on the Lunar New Year.

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