Sexagenary Index to Stem-Branch Converter

Description

Subtract one and take remainders modulo 10 and 12 for zero-based stem and branch indexes.

Gan-Zhi combines a ten-stem sequence with a twelve-branch sequence into a sixty-position traditional cycle. Cycle indexes, calendar dates and local clock labels are distinct inputs; the correct calendar assignment must be established separately.

Subtract one and take remainders modulo 10 and 12 for zero-based stem and branch indexes.

When to use this tool

Use Sexagenary Index to Stem-Branch Converter when you need an explicit traditional cycle-index mapping or step calculation.

How to use the tool and how it works

Enter ordinal. Use the units and conventions below.
Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
Read result. Expand result to inspect the returned fields.

Require ordinal 1-60. Subtract one and take remainders modulo 10 and 12 for zero-based stem and branch indexes.^[1]

The traditional sixty-position cycle starts at Jia-Zi. This tool returns indexes for an already supplied ordinal.^[2]

Input field	Meaning and units	Accepted input
ordinal	Ordinal	Required. Safe integer.

Output field	Interpretation	Returned shape
result	Object containing the calculated members; expand to inspect the fields below.	Required. Object.
result.stemIndex	Zero-based stem order: Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui.	Calculated result member: number.
result.branchIndex	Zero-based branch order: Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, Hai.	Calculated result member: number.

json

{
  "input": {
    "ordinal": 60
  },
  "output": {
    "result": {
      "stemIndex": 9,
      "branchIndex": 11
    }
  }
}

Limitations and assumptions

This maps an already supplied cycle position, not a Gregorian date. It does not provide calendrical or divinatory predictions.
Outputs are nested inside result. Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.

Alternative or Complementary methods

Consult the intended calendrical convention when deriving labels from dates. Keep local time, day boundaries and solar-term rules explicit rather than treating an index calculator as a calendar or predictive model.

References

Calculation and input contract: ganzhi/index-to-stem-branch — tool.io
Heavenly Stems and Earthly Branches — Hong Kong Observatory

Similar or alternative tools

Sexagenary Cycle Step Calculator
Find their shared position in the 60-step cycle, add steps modulo 60, and return ordinal and indexes.
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