stem-branchChinese Calendar & Stem-Branch Algorithms

The most accurate open-source Chinese calendar engine — solar terms verified to 1.05 seconds against JPL DE441 across 2,300 years. 10,392 terms computed over 7,000 years with zero failures.

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API Reference

神煞 Reference

1.05s Mean Accuracy

Validated against JPL Horizons (DE441) across 1,008 solar terms spanning 209–2493 CE. Outperforms sxwnl on all metrics. Equal or better for 98.9% of the 7,000-year timeline.

30 Almanac Flags (神煞)

Complete lookup tables for all almanac flags — 天乙貴人, 驛馬, 桃花, 華蓋, and 26 more. Every derivation rule documented with exact mappings.

First-Principles Astronomy

Full VSOP87D (2,425 terms) with DE441-fitted correction, IAU2000B nutation, and Newton-Raphson root finding. No lookup tables for solar terms.

Three Divination Systems (三式)

大六壬 (Six Ren), 奇門遁甲 (Mystery Gates), 紫微斗數 (Zi Wei Dou Shu) — all computed from first principles.

Seven Governors (七政四餘)

Chinese sidereal astrology — 7 planets + 4 lunar points placed in 28 lunar mansions and 12 palaces with aspects, dignities, and star spirits.