The basic unit of the Chinese calendar is 日 (Rì) which means ‘the sun’ and we translate it as ‘a day’. A day was defined as a period of time which involves the exchange between the light and the darkness. The astronomers then had to decide when exactly should a day start and end . At the end of the first millennia BC, it was decided that a day was to start at midnight.
Instead of months, the next unit of time stood for a cycle of ten days and was called 旬 (Xún). This notion is still present in modern Chinese, mainly with the phrases: 上旬 (ShàngXún) ‘first ten days of a month’, 中旬 (ZhōngXún) ‘middle ten days of a month’ and 下旬 (XiàXún) ‘last ten days of a month’.
The different days were named following the combination of ten heavenly stems 天干 (TiānGān) and twelve terrestrial branches 地支 (DìZhī). From the combination of these two, in the end 60 different days emerged. Don’t worry, this will all make sense in a minute.
So here are the ten heavenly stems:
- 甲 Jiǎ
- 乙 Yǐ
- 丙 Bǐng
- 丁 Dīng
- 戊 Wù
- 己 Jǐ
- 庚 Gēng
- 辛 Xīn
- 壬 Rén
- 癸 Guǐ
Interesting fact: characters 甲, 乙, 丙, 丁 are still used to mean A, B, C, D (for example in multiple choice questions).
The twelve terrestrial branches correspond to the animals in the Chinese zodiac cycle (this means that in one 60-year cycle, the zodiac would be repeated 5 times) .
- 子 Zǐ (rat)
- 丑 Chǒu (ox)
- 寅 Yín (tiger)
- 卯 Mǎo (hare, rabbit)
- 辰 Chén (dragon)
- 巳 Sì (snake)
- 午 Wǔ (horse)
- 未 Wèi (sheep)
- 申 Shēn (monkey)
- 酉 Yǒu (rooster)
- 戌 Xū (dog)
- 亥 Hài (pig)
The first day was 甲子 (JiǎZī, 1st stem, 1st branch), followed by 乙丑 (YǐChǒu, 2nd stem, 2nd branch), all the way to number ten which was 癸酉 (GuǐYǒu, 10th stem, 10th branch). The eleventh day was called 甲戌 (JiǎXū, 1st stem, 11th branch), followed by number 12 乙亥 (YǐHài, 2nd stem, 12th branch), number 13 丙子 (BǐngZǐ, 3rd stem, 1st branch), number 14 丁丑 (DīngChǒu, 4th stem, 2nd branch), all the way up to number 60 which was 癸亥 (GuǐHài, 10th stem, 12th branch). Afterwards the entire cycle was repeated.
The entire cycle is written here:
01.甲子 02.乙丑 03.丙寅 04.丁卯 05.戊辰 06.己巳 07.庚午 08.辛未 09.壬申 10.癸酉 11.甲戌 12.乙亥 13.丙子 14.丁丑 15.戊寅 16.己卯 17.庚辰 18.辛巳 19.壬午 20.癸未 21.甲申 22.乙酉 23.丙戌 24.丁亥 25.戊子 26.己丑 27.庚寅 28.辛卯 29.壬辰 30.癸巳 31.甲午 32.乙未 33.丙申 34.丁酉 35.戊戌 36.己亥 37.庚子 38.辛丑 39.壬寅 40.癸卯 41.甲辰 42.乙巳 43.丙午 44.丁未 45.戊申 46.己酉 47.庚戌 48.辛亥 49.壬子 50.癸丑 51.甲寅 52.乙卯 53.丙辰 54.丁巳 55.戊午 56.己未 57.庚申 58.辛酉 59.壬戌 60.癸亥
In Han Dynasty the cycle of 60, known as 干支 (GānZhī) started being used to count not just days, but also month and years. Thus 甲子 (JiǎZī) is also first year of they sixty-year cycle. The current 60-year cycle started on 2 Feb 1984. This means that the 15th year, or year 戊寅 (WùYín) in 1998. The 20th year in the cycle started in 2003. The year 2015 will start on the February 19, and is called 乙未 (YǐWèi).
And the table of 12 sings of Chinese zodiac through the years: