The Sexagenary Cycle
2026 BING WU 丙午 · 2025 YI SI 乙巳 · 60 JIAZI CALENDAR ENGINE
KEY TAKEAWAYS / TL;DR
- ◈The Sexagenary Cycle is the 60-pair Stem-Branch sequence used for Chinese years, months, days, hours, and Bazi pillars; 2026 is Bing Wu 丙午 and 2025 was Yi Si 乙巳.
- ◈A public zodiac year usually follows Chinese New Year, while many Bazi year pillars switch at Li Chun (Start of Spring), so boundary births need the stated method.
- ◈The 10 Heavenly Stems and 12 Earthly Branches create 60 valid same-polarity pairs, not 120; each exact pair repeats every 60 years.
Direct answer: a sexagenary year is a Chinese calendar year named by one Heavenly Stem and one Earthly Branch. The animal alone repeats every 12 years; the exact Stem-Branch pair repeats every 60 years.
For current-year queries: 2026 is Bing Wu 丙午 Fire Horse. For recent historical lookups, 2025 was Yi Si 乙巳 Wood Snake. General zodiac calendars usually begin the animal year at Chinese New Year, while many Four Pillars and Bazi systems use Li Chun around February 4 for the Year Pillar.
By the Numbers
- 60
- Stem-Branch Pairs
- Each exact year pair repeats once per 60 years.
- 2026
- Bing Wu 丙午
- Fire Horse year in the sexagenary sequence.
- 2025
- Yi Si 乙巳
- Wood Snake year in the sexagenary sequence.
2026 Chinese sexagenary year, 2025, and the Li Chun boundary
Use this quick map when a search result asks for the sexagenary year, zodiac year, or Bazi year boundary.
2026
Bing Wu 丙午 Fire Horse
Public zodiac: started February 17, 2026. Many Bazi charts switched at Li Chun around February 4.
2026 Fire Horse guide2025
Yi Si 乙巳 Wood Snake
Public zodiac: started January 29, 2025. Many Bazi charts switched at Li Chun around February 3-4. This is the 42nd Stem-Branch pair in the 60 Jiazi sequence.
2025 Chinese zodiac year guideFor someone born near early February, use the birth time, location, and the calendar rule stated by the Bazi calculator. This article explains the calendar framework, not a personal chart result.
HOW THE CYCLE WORKS
The Chinese calendar system uses two independent sequences that interlock like gears:
The 10 Heavenly Stems (天干) cycle through: Jiǎ, Yǐ, Bǐng, Dīng, Wù, Jǐ, Gēng, Xīn, Rén, Guǐ.
The 12 Earthly Branches (地支) cycle through: Zǐ, Chǒu, Yín, Mǎo, Chén, Sì, Wǔ, Wèi, Shēn, Yǒu, Xū, Hài.
On day 1, Stem #1 Jiǎ (甲) pairs with Branch #1 Zǐ (子) → Jiǎzǐ (甲子). On day 2, Stem #2 Yǐ (乙) pairs with Branch #2 Chǒu (丑) → Yǐchǒu (乙丑). After 10 days, the Stems restart at Jiǎ, but the Branches are only at #11 Xū (戌). After 12 days, the Branches restart, but Stems are at #3 Bǐng (丙). They only realign at their Least Common Multiple: day 60. Then the entire cycle repeats.
STEMS (10)
BRANCHES (12)
THE MATHEMATICS
It is crucial to understand why there are exactly 60 combinations, not 120 (10 × 12). The pairing rule locks Stems and Branches into same-parity tracks:
- ⚙Yang Stems (odd-numbered: Jiǎ 甲, Bǐng 丙, Wù 戊, Gēng 庚, Rén 壬) can ONLY pair with Yang Branches (odd-numbered: Zǐ 子, Yín 寅, Chén 辰, Wǔ 午, Shēn 申, Xū 戌).
- ⚙Yin Stems (even-numbered: Yǐ 乙, Dīng 丁, Jǐ 己, Xīn 辛, Guǐ 癸) can ONLY pair with Yin Branches (even-numbered: Chǒu 丑, Mǎo 卯, Sì 巳, Wèi 未, Yǒu 酉, Hài 亥).
- ∴This eliminates exactly half the possible combinations: 5 Yang Stems × 6 Yang Branches = 30, plus 5 Yin Stems × 6 Yin Branches = 30. Total: 60.
- ∴Because of this parity lock, you will never see a combination like Jiǎ-Chǒu 甲丑 (Yang Stem + Yin Branch) — it simply cannot exist in the system.
THE COMPLETE 60 JIAZI
APPLICATION IN BAZI
Your Bazi chart assigns one Stem-Branch pair to each of the four pillars:
Year Pillar (年柱)
Determines your Chinese zodiac animal and generational energy. Each animal repeats every 12 years, but each specific Stem-Branch combination repeats every 60 years — making your exact birth year pillar a once-in-60-years event.
Month Pillar (月柱)
Maps to the solar term of your birth month, reflecting seasonal energy. The Month Stem is derived from the Year Stem using a fixed formula.
Day Pillar (日柱)
Contains your Day Master (日主) — the single most important character in your chart. The day cycle repeats every 60 days, unbroken for millennia.
Hour Pillar (时柱)
Maps to the two-hour block of your birth. The Hour Stem is derived from the Day Stem. There are 12 hour branches per day, completing one micro-cycle.
THE VOID (旬空)
Because each "Xun" (旬, a 10-day period) only has 10 Stems but 12 Branches, two Branches are always left unmatched — they "fall into the void." In traditional reading, those branches are treated as temporarily suspended:
- ◈In Bazi: an element in the Void is often read as weaker or less stable in expression.
- ◈In Liuyao (I Ching divination): a voided line is often reconsidered when the calendar reaches its specific branch, called "Exiting the Void" (Chū Kōng 出空).
- ◈The Void is not permanent; when the calendar reaches the related branch, traditional readers reassess its strength and timing.
HISTORICAL SIGNIFICANCE
The Sexagenary Cycle is one of the oldest continuously-used timekeeping systems in human civilization. Oracle bone inscriptions from the Shang Dynasty (c. 1250 BCE) already record daily Stem-Branch notations, proving over 3,200 years of unbroken use.
Major events in Chinese history are named by their Jiazi year: the Xinhai Revolution (辛亥革命, 1911), the Jiawu War (甲午战争, Sino-Japanese War, 1894), and the Gengzi Incident (庚子事变, Boxer Rebellion, 1900).
| Stem | Element | Polarity |
|---|---|---|
| 甲 Jiǎ | Wood | Yang |
| 乙 Yǐ | Wood | Yin |
| 丙 Bǐng | Fire | Yang |
| 丁 Dīng | Fire | Yin |
| 戊 Wù | Earth | Yang |
| 己 Jǐ | Earth | Yin |
| 庚 Gēng | Metal | Yang |
| 辛 Xīn | Metal | Yin |
| 壬 Rén | Water | Yang |
| 癸 Guǐ | Water | Yin |
Source: Wikipedia — Sexagenary cycle; Chinese calendar; Oracle bone script