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BaZi fundamentals · Calendar system

What Is the Sexagenary Cycle? How the 60 Stem-Branch Pairs Work

The sexagenary cycle is a fixed sequence of 60 stem-branch pairs, beginning with Jia-Zi 甲子 and ending with Gui-Hai 癸亥. It is calendar notation used in the four pillars—not a list of 60 personality types or outcome predictions.

Written and edited by: Clarify

Editorial method: Clarify prepared and verified this guide using automated drafting and consistency checks against the cited sources and implemented calculation rules.

Updated: September 2, 2026

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The short answer

The sexagenary cycle is the repeating 60-step sequence formed by advancing one of the Ten Heavenly Stems and one of the Twelve Earthly Branches together. The first pair is Jia-Zi 甲子. After 60 steps, both lists return to their starting position, and the next step begins another cycle.

The Hong Kong Observatory describes the stems and branches as Gan-Zhi calendar notation and publishes the complete 60-pair table. Historical uses include designating years, months, days, and hours. In Four Pillars practice, the year, month, day, and hour are each represented by one of these pairs.

Why are there 60 pairs instead of 120?

There are ten stems and twelve branches, but the cycle does not combine every stem with every branch. Both lists advance one place at the same time. Yang stems therefore meet the six yang branches, and yin stems meet the six yin branches.

The two lists return to their shared starting position after the least common multiple of 10 and 12: 60 steps. This produces 60 ordered pairs, not the 120 combinations that would appear if every stem were matched freely with every branch.

A quick check

Jia 甲 is the first stem and Zi 子 is the first branch, so the cycle opens with Jia-Zi 甲子. Yi 乙 and Chou 丑 advance together to form the second pair. The same rule continues through Gui-Hai 癸亥 at position 60.

The complete 60-pair sequence

The list is numbered by position in the cycle. Romanization is included as a reading aid.

  1. 甲子Jia-Zi
  2. 乙丑Yi-Chou
  3. 丙寅Bing-Yin
  4. 丁卯Ding-Mao
  5. 戊辰Wu-Chen
  6. 己巳Ji-Si
  7. 庚午Geng-Wu
  8. 辛未Xin-Wei
  9. 壬申Ren-Shen
  10. 癸酉Gui-You
  11. 甲戌Jia-Xu
  12. 乙亥Yi-Hai
  13. 丙子Bing-Zi
  14. 丁丑Ding-Chou
  15. 戊寅Wu-Yin
  16. 己卯Ji-Mao
  17. 庚辰Geng-Chen
  18. 辛巳Xin-Si
  19. 壬午Ren-Wu
  20. 癸未Gui-Wei
  21. 甲申Jia-Shen
  22. 乙酉Yi-You
  23. 丙戌Bing-Xu
  24. 丁亥Ding-Hai
  25. 戊子Wu-Zi
  26. 己丑Ji-Chou
  27. 庚寅Geng-Yin
  28. 辛卯Xin-Mao
  29. 壬辰Ren-Chen
  30. 癸巳Gui-Si
  31. 甲午Jia-Wu
  32. 乙未Yi-Wei
  33. 丙申Bing-Shen
  34. 丁酉Ding-You
  35. 戊戌Wu-Xu
  36. 己亥Ji-Hai
  37. 庚子Geng-Zi
  38. 辛丑Xin-Chou
  39. 壬寅Ren-Yin
  40. 癸卯Gui-Mao
  41. 甲辰Jia-Chen
  42. 乙巳Yi-Si
  43. 丙午Bing-Wu
  44. 丁未Ding-Wei
  45. 戊申Wu-Shen
  46. 己酉Ji-You
  47. 庚戌Geng-Xu
  48. 辛亥Xin-Hai
  49. 壬子Ren-Zi
  50. 癸丑Gui-Chou
  51. 甲寅Jia-Yin
  52. 乙卯Yi-Mao
  53. 丙辰Bing-Chen
  54. 丁巳Ding-Si
  55. 戊午Wu-Wu
  56. 己未Ji-Wei
  57. 庚申Geng-Shen
  58. 辛酉Xin-You
  59. 壬戌Ren-Xu
  60. 癸亥Gui-Hai

How the cycle appears in a BaZi chart

A Four Pillars chart contains four stem-branch pairs: one each for year, month, day, and hour. Those four pairs produce the “eight characters” in the name BaZi.

  • Year Pillar: one stem plus one branch.
  • Month Pillar: one stem plus one branch.
  • Day Pillar: one stem plus one branch.
  • Hour Pillar: one stem plus one branch when birth time is known.

The pair is a calendar identifier. Traditional interpretation may attach element, polarity, hidden-stem, or relationship language to its parts, but the pair itself does not prove personality, compatibility, health, wealth, or future events.

What Clarify actually calculates

Clarify calculates the four pillars separately under declared rules. The current implementation uses the Li Chun boundary for the Year Pillar, solar-longitude segments for the Month Pillar, the submitted civil date for the Day Pillar, and corrected true-solar clock time for the Hour Pillar when time and location are available.

This separation matters near a boundary. A changed input can alter one pillar without changing every pillar. If birth time is unknown, Clarify does not invent an Hour Pillar.

For the stable definitions behind these fields, see the Knowledge Base pages on Heavenly Stems, Earthly Branches, Year, Month, Day, and Hour Pillars, and the Li Chun year boundary.

Two related pages answer narrower questions: Sexagenary Day Cycle Validation explains how the day cycle is checked, while the NaYin Table for the Sixty JiaZi records a separate traditional classification. Neither replaces this overview of the cycle itself.

Four common mistakes

  1. Treating the cycle as 60 personality types. It is first a calendar sequence.
  2. Using only the zodiac animal. The animal corresponds to the branch; a full pair also has a stem.
  3. Reading one pair as a whole chart. A BaZi chart contains four pairs plus the relationships among them.
  4. Assuming one boundary changes everything. Review the Year, Month, Day, and Hour Pillars separately.

Learning boundary

BaZi is a traditional cultural framework, not a scientific diagnostic or forecasting method. Use this article to understand the notation, not to make medical, legal, financial, relationship, or safety decisions.

Sources and editorial method

  1. Hong Kong Observatory: Heavenly Stems and Earthly Branches — the ten stems, twelve branches, complete 60-pair table, and their calendar use.
  2. OpenFate: What Is the Sexagenary Cycle? — authorized reference article used as the starting topic map.
  3. Clarify Editorial Methodology — how traditional explanations, implemented calculation rules, and unsupported conclusions are kept separate.

This Clarify guide is an original rewrite built from an authorized reference snapshot. Its wording, 60-pair verification, calculation-boundary explanation, mistake checks, and safety boundary were checked specifically for this topic.