Countries in the East Asian cultural sphere (China, Korea, Japan, Vietnam, and their diaspora) have traditionally used specific methods of determining a person's numerical age based not on their birthday but on the calendar year. These methods see only limited use in certain contexts and areas, mainly in South Korea and Taiwan. However, in 2022, the government of South Korea announced plans to switch from the Korean age system to the international age system. A person's Korean age will always differ from their international age by one or two years.
In China, where the system originated millennia ago, people are considered to be one "year old" at birth (one sui 嵗/岁), and on New Year's Day of the lunar calendar, another year is added to their age. In other words, age is counted with ordinal numbers, not cardinal numbers; also, age is counted from the lunar new year, not from the date of birth. The Korean system uses the Gregorian calendar.
South Koreans also use a third system sometimes called "year age", especially for administrative purposes, determined by the birth year and the current year. To put it simply, the equation is given by marking a person to be zero years old at birth, or
Eastern Mongolia has a different system for measuring a person's age, which is based on the number of lunar cycles that have passed (since birth for boys; girls are measured from conception).
See also: Chinese first birthday
Currently in China and in Chinese societies around the world, the term sui when used all by itself can be ambiguous. In most contexts, such as the age on legal documents, it is equivalent to the English "years old." Thus, in China, where the legal age of alcohol consumption is 18 sui, one is not legally permitted to drink alcohol until after their 18th birthday. However, in some contexts, such as in determining age for fortune-telling purposes, or in reading pre-modern texts, one must distinguish between the traditional way of calculating age and the modern way adopted from the West.
In pre-modern times, sui was calculated from the time of birth. A person was one sui as soon as they were born. At the Lunar new year, they turned two sui, and every subsequent new year after that, they were one more sui. Thus, by traditional reckoning, sui does not exactly mean "years old". To differentiate today, the term xu 虛/虚 or mao 毛 (both meaning nominal) is added to the word sui.
In many Chinese societies around the world, a child's horoscope is calculated at birth and is considered relevant throughout their life. The horoscope is calculated using the traditional sui (xu sui). 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. Thus, for a child born in June of the year 2000, a year of the dragon, the first fan tai sui year would occur in the next dragon year, which would begin on Lunar new year in the year 2012, when the child turns 13 sui. By modern reckoning, the child would be 11 years old at the beginning of the year and turn 12 years old in June. Therefore, the modern way of reckoning age does not correspond to the horoscope. Using the traditional reckoning, the child in the example is 13 sui for the entirety of the fan tai sui year.
If one needs to distinguish the Western adopted terminology that is in general use now, xu sui is contrasted with shi sui 實歲/实岁 (or zhou sui 周嵗/周岁), but outside of astrological uses, the need for such a contrast today is rare. One must be careful, however, when calculating ages in pre-modern times. A figure listed as 69 sui during the Song dynasty, for example, would not be 69 years old and would instead be either 67 or 68. The exact age, by modern reckoning, would be impossible to know just from the sui alone, without knowing the actual year of birth by the Gregorian calendar.
When a child has survived one month of life (29 days, if using Lunar month reckoning), a mun yuet (Chinese: 滿月; pinyin: mǎnyuè; Jyutping: mun5 jyut6) celebration can be observed, in which duck or chicken eggs dyed red are distributed to guests to signify fertility.
East Asian age reckoning, both linguistically and in practice, follows the example of China (see § China) as the vast majority of Taiwanese people are ethnically Chinese. Unlike the Chinese however, the Taiwanese more widely use the East Asian age reckoning in a variety of social contexts and the term sui (歲) less ambiguously refers to ones age according to this system. While birthdays are increasingly celebrated according to the Gregorian calendar, the traditional age reckoning is retained (e.g. Su Beng's centennial was celebrated to honor his November 5th, 1918 birth in the Gregorian calendar in 2017, not 2018). Furthermore, Taiwanese, like South Koreans, do not add year to their age on their birthdays but on New Year's Day (in the case of Taiwan, on the Lunisolar Chinese calendar New Year and not the Gregorian one as in Korea).
Koreans who use the traditional system refer to their age in units called sal (살), using Korean numerals in ordinal form. Thus, a person is one sal (han sal [한살]) during the first calendar year of life, and ten sal during the tenth calendar year. Sal is used for native Korean numerals, while se (세; 歲) is used for Sino-Korean. For example, seumul-daseot sal (스물다섯 살) and i-sib-o se (이십오 세; 二十五 歲) both mean 'twenty-five-year-old'. If the international system is used (man-nai [만나이]), then the age would be man seumul-daseot sal (만 스물다섯 살). South Koreans speaking of age in the colloquial context will almost without question be referring to the traditional system, unless the man qualifier is used.
The 100th day after a baby was born is called baegil (백일, 百日) which literally means "a hundred days" in Korean, and is given a special celebration, marking the survival of what was once a period of high infant mortality. The first anniversary of birth named dol (돌) is likewise celebrated, and given even greater significance. South Koreans celebrate their birthdays, even though every South Korean gains one sal on New Year's Day. Because the first year comes at birth and the second on the first day of the New Year, children born, for example, on December 31st are considered to become two-year-olds the very next day, New Year's Day (of the Gregorian, not the Korean calendar).
Hence, everyone born on the same calendar year effectively has the same age and can easily be calculated by the formula: Age = (Current Year − Birth Year) + 1
In modern South Korea the traditional system is used alongside the international age system which is referred to as man-nai (만나이) in which "man" (만) means "full" or "actual", and nai (나이) meaning "age". For example, man yeol sal means "full ten years", or "ten years old" in English. The Korean word dol means "years elapsed", identical to the English "years old", but is only used to refer to the first few birthdays. Cheotdol or simply dol refers to the first Gregorian-equivalent birthday, dudol refers to the second, and so on.
The traditional system has not been used in modern North Korea since the 1980s. South Korea is now one of only two countries (the other being Taiwan) that widely uses the East Asian age, which is consequently sometimes referred as "Korean age".
A Korean birthday celebration by the Lunar calendar is called eumnyeok saeng-il (음력 생일, 陰曆生日) and yangnyeok saeng-il (양력 생일, 陽曆生日) is the birthday by the Gregorian calendar. In the past, most people used the Lunar calendar (eumnyeok saeng-il) to tell their birthdays rather than the Gregorian calendar (yangnyeok saeng-il), but nowadays Koreans, especially young generations, tend to use yangnyeok saeng-il for telling their birth dates.
For official government uses, documents, and legal procedures, the international system is used. Regulations regarding age limits on beginning school, as well as the age of consent, are all based on this system (man-nai). The age qualifier for tobacco and alcohol use is actually similar to, but distinct from the East Asian reckoning system. A person is allowed tobacco and alcohol if it is after January 1 of the year one turns 19 (post-birth age). This is the "year age", which is basically (Korean age – 1), or when a person's Korean age is 20.
Calls to remove the system intensified in early 2022 due to the COVID-19 pandemic, as inconsistent use of the two age systems created conflicts in the eligibility criteria for COVID-19 vaccines and a vaccine passport rule; some residents were being deemed ineligible for vaccination, but at the same time subject to a proof of vaccination requirement for certain establishments. 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 standard international age system.
The traditional Japanese system of age reckoning, or kazoedoshi (数え年, lit. "counted years"), which incremented one's age on New Year's Day, was rendered obsolete by law in 1902 when Japan officially adopted the modern age system, known in Japanese as man nenrei (満年齢). However, the traditional system was still commonly used, so in 1950 another law was established to encourage people to use the modern age system.
Today the traditional system is used only by the elderly and in rural areas. Elsewhere its use is limited to traditional ceremonies, divinations, and obituaries.[original research?]
Japanese uses the word sai (歳 or 才) as a counter word for both the traditional and modern age system.
Because of the idea of yakudoshi or unlucky years, kanreki is a special occurrence for celebrating 60 years of life, meaning one has returned to the same combination of zodiacal symbols that governed the year of one's birth.
Having been influenced by Chinese culture, the ancient Vietnamese also used this system and, despite not being the official age on papers and in daily usages at the present, the East Asian age is still in limited use by adults, especially old people in rural areas. However, this age system is not really familiar to the younger generation. In Vietnam, it is called tuổi mụ ('her age'), tuổi ta (literally 'our age', contrasting with Western age tuổi Tây) or tuổi âm ('lunar-calendar age').
Koreans are considered one year old at birth and added another year at New Year's....some Koreans may use American age counting convention while others still follow Korean convention. To eliminate this confusion, Korean asked '만나이(Man-nai)': the same as the U.S. age counting convention.
시기나 햇수를 꽉 차게 헤아림을 이르는 말.(trans. The word refers to calculating full years or periods.
I. (명사) 어린아이가 태어난 날로부터 한 해가 되는 날. (II ) 1. 생일이 돌아온 횟수를 세는 단위. 주로 두세 살의 어린아이에게 쓴다. 2. 특정한 날이 해마다 돌아올 때, 그 횟수를 세는 단위.
최근 이승엽의 아버지 이춘광씨는 보통 양력생일을 치르는 요즘의 추세와 달리 이승엽의 음력 생일(1976년 8월18일)을 치르는 사연을 밝혀 화제가 됐다 (trans. It was a recent topic that Lee Chun-gwang, the father of Lee Seung-Yeop, revealed the reason why Lee Seung-Yeop takes his lunar birthday on August 18, 1976 instead of the solar birthday as opposed to the current trend.)
한국의 경우 만 20세로 성년이 되며(민법 제4조)...연령의 계산은 민법 제155조 이하의 규정에 의하나, 출생일을 산입한다(동법 제158조). 1977년의 민법 개정으로 혼인에 의한 성년의제(成年擬制)의 제도를 도입했다..대통령선거법·국회의원선거법·국민투표법·지방자치법·지방의회의원선거법·미성년자보호법 등에서는 이 원칙이 적용되지 않는다.
"청소년" 이란 만 19세 미만인 사람을 말한다. 다만, 만 19세가 되는 해의 1월 1일을 맞이한 사람은 제외한다.