At a glance
- Period
- Sixty steps
- Arithmetic
- Advance both sequences together
Definition and terminology
The cycle starts Jia-Zi, Yi-Chou and Bing-Yin and ends Gui-Hai. Both sequences advance together, giving sixty permitted pairs rather than all 120 theoretical combinations. Parity is preserved, so Jia-Chou is excluded. Years and days can both carry these labels, but their cycles are distinct.
Structure and rules
Sixty is the least common multiple of ten and twelve. With a reliable starting point, modular arithmetic gives later pairs. Practical day naming still needs a trusted epoch. Month boundaries must be specified, month stems derive from year stems, and hour stems derive from day stems in the traditional conversion scheme.
Worked reading
In a teaching sequence beginning Jia-Zi, the second pair is Yi-Chou, the eleventh Jia-Xu and the thirteenth Bing-Zi. Stems and branches return at different intermediate steps; both reset together at step sixty-one. Separate columns make the procedure transparent. A fictional starting point should never be used to date an actual event.
Context and limits
Year boundaries can differ by use: lunar New Year and the Start of Spring are both encountered, while natal practice commonly uses solar-term boundaries. Day rollover at 23:00 versus midnight is another convention. Calendar conversion is checkable; a correct conversion does not independently validate interpretations of a person’s future.
References & further reading
Historical sources document ideas and rules of their time, not empirical proof of predictive accuracy. Source notes identify the nature and scope of each reference.
- Hong Kong Observatory: Heavenly Stems and Earthly BranchesInstitutional / reference source
Official calendar reference for sequences and double hours; does not validate natal divination.