What does 을유년 mean?

Here is an old post from January 2005 that I forgot I had posted. I am reposting it for those who might find it interesting.
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2005 is the "Year of the Chicken," which is translated in Korean as "닭의 해." However, Koreans also call this year, 을유년(乙酉年). Though the "year of the chicken" will come around again in twelve years, 을유년 will not recycle for another sixty years. Here is the reason.

Koreans traditionally name a new year by combining one of ten "heavenly stems" (天干 - 천간) with one of twelve "earthly branches" (地支 - 지지). The heavenly stems represent the ten mythical suns that take turns warming the earth while the "earthly branches" represent the twelve moons of the year, which happen to be named after animals. This naming system is called 간지(干支), "stems & branches." Here is a list of the 간지.

Heavenly Stems (천간)

1. 갑 (甲)
2. 을 (乙)
3. 병 (丙)
4. 정 (丁)
5. 무 (戊)
6. 기 (己)
7. 경 (庚)
8. 신 (辛)
9. 임 (壬)
10. 계 (癸)

Earthly Branches (지지)

1. 자 (子) - 쥐 rat
2. 축 (丑) - 소 cow
3. 인 (寅) - 범 tiger
4. 묘 (卯) - 토끼 rabbit
5. 진 (辰) - 용 dragon
6. 사 (巳) - 뱀 snake
7. 오 (午) - 말 horse
8. 미 (未) - 양 sheep
9. 신 (申) - 원숭이 monkey
10. 유 (酉) - 닭 chicken
11. 술 (戌) - 개 dog
12. 해 (亥) - 돼지 pig

In the Korean year-naming system, one "heavenly stem" is combined with one "earthly branch." The "heavenly stem" comes first. For example, the name for 2005 is 을유년. 을 is the "stem," 유 is the "branch," and 년 is the Korean word for "year." If you want to learn the naming system, you must first memorize the two lists since the stems and branches must be combined in the sequential order of their specific lists.

Below is the list of the sixty combinations in a sixty year cycle.

The 60 간지 Combinations (also know as 60 갑자)

갑자(甲子), 을축(乙丑), 병인(丙寅), 정묘(丁卯), 무진(戊辰), 기사(己巳), 경오(庚午), 신미(辛未), 임신(壬申), 계유(癸酉), 갑술(甲戌), 을해(乙亥), 병자(丙子), 정축(丁丑), 무인(戊寅), 기묘(己卯), 경진(庚辰), 신사(辛巳), 임오(壬午), 계미(癸未), 갑신(甲申), 을유(乙酉), 병술(丙戌), 정해(丁亥), 무자(戊子), 기축(己丑), 경인(庚寅), 신묘(辛卯), 임진(壬辰), 계사(癸巳), 갑오(甲午), 을미(乙未), 병신(丙申), 정유(丁酉), 무술(戊戌), 기해(己亥), 경자(庚子), 신축(辛丑), 임인(壬寅), 계묘(癸卯), 갑진(甲辰), 을사(乙巳), 병오(丙午), 정미(丁未), 무신(戊申), 기유(己酉), 경술(庚戌), 신해(辛亥), 임자(壬子), 계축(癸丑), 갑인(甲寅), 을묘(乙卯), 병진(丙辰), 정사(丁巳), 무오(戊午), 기미(己未), 경신(庚申), 신유(辛酉), 임술(壬戌), 계해(癸亥)

Notice that the first combination in the above list is "갑자(甲子)," which is a combination of the first character in the "heavenly stem" list and the first character in the "earthly branch" list. The second combination is 을축(乙丑), which is the second character in the "heavenly stem" list and the second character in the "earthly branch" list. The sequential pairing continues until one reaches the bottom of a list, at which point one returns to the top of of the list and continues.

Since the "heavenly stem" list has ten characters, and the "earthly branch" list has twelve, the two lists will get out of sequence after the first pairing cycle. For example, when the "heavenly stem" list recycles back to number one, 갑(甲), the "earthly branches" list will be continuing on to number eleven, 술(戌). Therefore, the eleventh pairing in the 60-combination list is 갑술(甲戌). The combinations in red show where the "heavenly branch" list recycles back to 갑(甲). The recycling in both lists continues until the lists recycle all the way back to the beginning combination, 갑자(甲子), which occurs after sixty combinations.

In Korean culture, this sixty-year cycle symbolizes one lifetime. If a Korean lives long enough to return to the beginning of his life cycle, his family and friends usually celebrate it with a banquet known as 환갑 잔치, which literally means "The Returning to "kap" Banquet."

If you are like me, you may have asked yourself, "Shouldn't there be 120 combinations of 'stems' and 'branches' instead of only sixty since 10 stems times 12 branches equals 120?" Well, the answer is "no," and here is the reason.

First, ask yourself this question. How many combinations would there be if there were an equal number of stems and branches, for example, ten each? The answer is "ten combinations." The reason is that after each list reached number ten, they would both recycle, in sequence, back to number one, returning to the same beginning combination and ending the cycle. However, when there are ten stems and twelve branches, the two lists will get out of sync after the first cycle because when the ten-stem list recycles back to number one, the twelve-branch list continues to number eleven, creating a 1-11 combintion. The next combination will be a 2-12 combination, after which the branch-list also recycles back to 1, meaning the next combination is a 3-1 combination. At this point the two lists are two characters out of sync. When the longer branch list recycles a second time, the two lists will then be four characters out of sync (a 5-1 combination). This pattern continues until the two lists finally recycle back to the beginniing combination (1-1).

Because the difference in length between the two lists is an even number (two characters), the number combinations will always be either even-even or odd-odd, never odd-even or even-odd. This results in there only being sixty combinations instead of 120.

If you are wondering how you will ever learn all the different combinations, stop wondering because you do not have to. Here is a trick that can help you figure out the combinations.

Since there are ten "heavenly stems," the same stem will always correspond to the same last number in a year. For example, any year that ends with "4" (e.g. 2004) will always begin with 갑, and any year that ends with "5" (e.g. 2005) will begin with 을, the second character in the sequence. If you know the sequence of the ten "heavenly stems", then it should be easy to remember the first character of any year. And if you know the sequence of the "earthly branches," together with the earthly branch you were born under, you can add or subtract in multiples of twelve to figure out the second character. Just use your birthday as the starting point. For example, I know that the 간지 name for 1967 is 정미년 because, first of all, any year that ends in 7 always starts with 정, and, second of all, 1967 is twelve years ahead of 1955, which was "the year of the sheep"(미) and also the year I was born.

Why bother learning the 간지 naming system? Well, if you are a student of Korean history, it can help you remember the names and dates of historic Korean events since Koreans often refer to such events by the name of the year it happened. The following historic events are just a few examples. There are many more.

• 임진왜란 (***2)
• 신미양요 (***1)
• 갑신정변 (***4)
• 갑오개혁 (***4)
• 을미사변 (***5)
• 을사조약 (***5)