Description
Return [2(dayStemIndex modulo 5)+hourBranchIndex] modulo 10.
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.
Return [2(dayStemIndex modulo 5)+hourBranchIndex] modulo 10.
When to use this tool
Use Hour Heavenly Stem Calculator when you need an explicit traditional cycle-index mapping or step calculation.
How to use the tool and how it works
- Enter dayStemIndex, hourBranchIndex. 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 dayStemIndex 0-9 and hourBranchIndex 0-11. Return [2(dayStemIndex modulo 5)+hourBranchIndex] modulo 10.1
The hour-stem sequence depends on the day stem and the supplied hour branch.2
| Input field | Meaning and units | Accepted input |
|---|---|---|
| dayStemIndex | Zero-based stem order: Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui. | Required. Safe integer. |
| hourBranchIndex | Zero-based branch order: Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, Hai. | Required. Safe integer. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| result | Object containing the calculated members; expand to inspect the fields below. | Required. Object. |
| result.hourStemIndex | Zero-based stem order: Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui. | Calculated result member: number. |
{
"input": {
"dayStemIndex": 0,
"hourBranchIndex": 0
},
"output": {
"result": {
"hourStemIndex": 0
}
}
}Limitations and assumptions
- The day stem and hour branch must already be determined under a compatible tradition; no date boundary or true-solar-time correction is selected.
- 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/hour-stem-from-day-stem — tool.io
-
Heavenly Stems and Earthly Branches — Hong Kong Observatory
Similar or alternative tools
- Shichen Double-Hour Calculator
Compute branchIndex as floor(((hour+1) modulo 24)/2), and return its start/end hours and midnight-crossing flag.
- Month Heavenly Stem Calculator
Return [2(yearStemIndex modulo 5)+2+((monthBranchIndex-2) modulo 12)] modulo 10.