East Asian age reckoning

Historical records from China, Japan, Korea, and Vietnam have usually been based on these methods, whose specific details have varied over time and by place.

In this system, one's age is not a calculation of the number of calendar years (年, nián) since birth but a count of the number of these Jovian stars (simplified Chinese: 岁; traditional Chinese: 歲; pinyin: suì) whose influence one has lived through.

By the Song dynasty, this system—and the extra importance of the sixtieth birthday produced by its combination with the sexagenary cycle—had spread throughout the Sinosphere.

The Republic of China partially modernized the system during their own reforms, which were continued by the Communists after the Chinese Civil War.

In many Chinese societies around the world, a child's horoscope is calculated at birth and is considered relevant throughout their life.

This becomes important, for example in calculating a person's fan tai sui 反太歲/反太岁, which occurs after every twelve-year zodiac cycle.

For example, seumuldaseot sal (스물다섯 살) and isibo se (이십오 세; 二十五歲) both mean 'twenty-five-year-old'.

South Koreans speaking of age in the colloquial context will almost without question be referring to the traditional system,[according to whom?]

The Korean word dol means 'years elapsed', identical to the English "years old", but is only used to refer to the first few birthdays.

[18] A Korean birthday celebration by the Lunar calendar is called eumnyeok saengil (Korean: 음력 생일; Hanja: 陰曆生日) and yangnyeok saengil (양력 생일; 陽曆生日) is the birthday by the Gregorian calendar.

[15][20] The age qualifier for tobacco and alcohol use is actually similar to, but distinct from the East Asian reckoning system.

In April 2022, the transition committee of president-elect Yoon Suk-yeol stated that the government planned to amend the Civil Code and other relevant legislation to switch to the international age system.

[23] On 8 December 2022, the National Assembly passed a bill that prohibits the usage of traditional ages on official documents.

[26] Due to how intertwined the previous system was with age hierarchies,[26] it's also predicted that it will help combat the hierarchical and ageist nature of South Korean society.

[28] Despite the conversion, the old system will still be retained for a few aspects, including the year students enter elementary school and the age individuals can purchase alcohol or cigarettes or join mandatory military service.