Lee Jung-hee was set to turn 60 next year but South Korea dropped its traditional age counting system on Wednesday, so the Seoul-based housewife just got a year younger – and she's thrilled.

South Korea is the last East Asian country to officially still use a method of calculating age that determines babies are aged one at birth, counting their months in the womb as their first year of life.

Under that system everyone gets a year older with the turn of the year rather than on their actual birthday, meaning a baby born on December 31 would be considered two years old on January 1 in Korean age.

From Wednesday South Korea will use the international system that calculates age according to a person's actual date of birth, meaning everyone will officially become a year or two younger.

"It feels good," Lee, a Seoul-based housewife, said. "For people like me, who were supposed to turn 60 next year, it makes you feel like you're still young," she laughed.

China, Japan, and even North Korea dropped the system decades ago but it has endured in the South, even as the land that gave the world K-pop and kimchi played a larger role on the international stage.

"It's confusing when a foreigner asks me how old I am as I know they mean international age, so I have to do some calculations," office worker Hong Suk-min said.

Hong added, after a thoughtful pause, that he was 45 in international age and 47 under the Korean system.

The official change will have limited practical impact: many legal and administrative functions, including the age listed on a passport, the age at which one can be prosecuted as a juvenile, retirement benefits, or healthcare services, already uses date-of-birth rather than Korean age.

The government hopes the change will ease confusion and cites, for example, the issue of older Koreans who may believe they are eligible for pensions and free travel benefits several years before they legally are. (AFP)