At a glance
- Duration
- Commonly ten years per pair
- Sequence
- Advance from month pillar in chosen direction
Definition and terminology
Decadal cycles commonly advance from the month pillar, with each pair governing roughly ten years in the tradition. Annual signs identify a studied year. Starting age is calculated from a birth-to-term interval, so it is not always zero. Distinguish cycle labels, ages and calendar dates, including nominal versus completed-age conventions.
Structure and rules
A common direction rule combines year-stem polarity with traditional sex categories, while alternatives use other reference stems. A familiar conversion treats three interval days as one starting year, but boundary and fraction rules vary. Establish the temporal layer first, then compare relationships with the natal chart. Publish the calculation assumptions with any dates.
Worked reading
With Yi-Chou as a hypothetical month pillar, forward cycles begin Bing-Yin and Ding-Mao; backward cycles begin Jia-Zi and Gui-Hai. A nine-day interval under a three-days-per-year convention gives a starting age of three. These are sequence and conversion exercises, not predictions that a particular event occurs at that age.
Context and limits
Calling a cycle a ten-year tendency does not make every day identical or specify one annual event. Different calculations can change transition dates, so uncertain records need ranges. Learning temporal layering is distinct from validating it. Keep actual event records separate from retrospective interpretation rather than selecting only apparently matching anecdotes.
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.
- 《三命通会》（四库全书本）Primary / tradition source
Public-domain natal-divination compilation with historical editorial criticism; rule documentation, not modern validation.
- Hong Kong Observatory: Heavenly Stems and Earthly BranchesInstitutional / reference source
Official calendar reference for sequences and double hours; does not validate natal divination.