Last week, I came across a foreign girl in a Chinese tea ware shop. She knew some Chinese but not much, so I helped her communicate with the shop owner, an elderly gentleman.
She knew her zodiac sign but was confused by the Chinese characters next to the zodiac animals on the little cups.
Well, that’s a bit complicated because it involves the system of 天干地支 (tiān gān dì zhī) — Heavenly Stems and Earthly Branches. It was used in ancient Chinese astronomy and calendars to mark years, months, days, and hours. It was also widely used in divination, counting, and naming.
Now, back to the Chinese zodiac: the twelve zodiac animals repeat every twelve years. So, if two different years are 12 years apart (e.g., 2014 and 2026), are they exactly the same?
The answer is no.
The reason lies in the combination of the ten Heavenly Stems and the twelve Earthly Branches. When you combine them sequentially—matching the first stem with the first branch, the second with the second, and so on—it takes sixty years for the same combination to reappear. This is known as the sexagenary cycle, or a full “甲子 (jiǎ zǐ)” cycle.
I know the math might be a little confusing. Why is it 60 years instead of 120?
Well, there’s a traditional rule: Yin pairs with Yin, and Yang pairs with Yang. In mathematical terms, it simply means odd numbers pair with odd numbers, and even numbers pair with even numbers.
Take a look at the ten Heavenly Stems (甲 jiǎ, 乙 yǐ, 丙 bǐng, 丁 dīng, 戊 wù, 己 jǐ, 庚 gēng, 辛 xīn, 壬 rén, 癸 guǐ) and the twelve Earthly Branches (子 zǐ, 丑 chǒu, 寅 yín, 卯 mǎo, 辰 chén, 巳 sì, 午 wǔ, 未 wèi, 申 shēn, 酉 yǒu, 戌 xū, 亥 hài). According to this rule, we have years like Jiǎ Zǐ and Yǐ Chǒu, but we never have Jiǎ Chǒu or Yǐ Zǐ. Does that make sense?
So, here’s a quick test for you: if this year is the year of the Bǐng Wǔ Horse, do you know what next year will be?