stembranch

Astronomical Chinese calendar, 四柱八字, and divination computation for TypeScript. Solar terms, lunar calendar, stem-branch cycles, Eight-Character analysis, and three classical divination systems — all from first principles.

import { computeFourPillars, computeMajorLuck, dailyAlmanac } from 'stembranch';

const pillars = computeFourPillars(new Date(2024, 1, 10, 14, 30));
// → { year: {stem: '甲', branch: '辰'}, month: {stem: '丙', branch: '寅'},
//     day:   {stem: '壬', branch: '午'}, hour:  {stem: '丁', branch: '未'} }

const luck = computeMajorLuck(new Date(1990, 6, 15), 'male');
// → { direction: 'forward', startAge: 8, periods: [{pillar: {stem:'甲', ...}, startAge: 8, endAge: 17}, ...] }

Install

npm install stembranch

Zero production dependencies. Self-contained VSOP87D (2,425 terms) and Meeus Ch. 49 new moon algorithms with sub-second solar term precision and full lunar calendar computation.

Quickstart

Four Pillars (四柱八字)

import { computeFourPillars } from 'stembranch';

const pillars = computeFourPillars(new Date(2024, 1, 10, 14, 30));
// → year: 甲辰, month: 丙寅, day: 壬午, hour: 丁未

Luck Periods (大運)

import { computeMajorLuck, computeMinorLuck, getLuckDirection } from 'stembranch';

// 大運: 10-year periods from month pillar
const luck = computeMajorLuck(new Date(1990, 6, 15), 'male', 8);
// → direction: 'forward', startAge: 8
// → periods: [{pillar: 甲申, startAge: 8}, {pillar: 乙酉, startAge: 18}, ...]

// 小運: year-by-year from hour pillar
const minor = computeMinorLuck({stem: '甲', branch: '子'}, 'forward', 1, 10);
// → [{age: 1, pillar: 乙丑}, {age: 2, pillar: 丙寅}, ...]

Daily Almanac (日曆總覽)

One call, everything at once — four pillars, lunar date, solar terms, zodiac, day fitness, flying stars, almanac flags, Six Ren chart, eclipses, and element analysis:

import { dailyAlmanac } from 'stembranch';

const a = dailyAlmanac(new Date(2024, 5, 15));
// a.pillars      → year/month/day/hour stem-branch pairs
// a.lunar        → { year: 2024, month: 5, day: 10, isLeapMonth: false }
// a.dayFitness   → { fitness: '成', auspicious: true }
// a.almanacFlags → [{ name: '天乙貴人', english: 'Heavenly Noble', ... }, ...]
// a.sixRen       → { method: '賊剋', lessons: [...], ... }
// a.flyingStars  → { year: {...}, month: {...}, day: {...}, hour: {...} }

Divination Systems (三式)

import { computeSixRenForDate, computeQiMenForDate, computeZiWei } from 'stembranch';

// 大六壬
const sixRen = computeSixRenForDate(new Date(2024, 5, 15, 14));
// → { plates, lessons, transmissions, method: '賊剋', generals, ... }

// 奇門遁甲
const qimen = computeQiMenForDate(new Date(2024, 5, 15));
// → { earthPlate, heavenPlate, stars, doors, deities, escapeMode: '陰遁', juShu: 6, ... }

// 紫微斗數
const chart = computeZiWei({ year: 1990, month: 8, day: 15, hour: 6, gender: 'male' });
// → { palaces: [...14 major stars placed...], siHua, elementPattern, taiSuiIndex, ... }

Design Decisions

Year boundary: 立春 (Start of Spring), not January 1

The 干支 year starts at 立春, the moment the sun reaches ecliptic longitude 315°. This falls around February 3-5 each year. A person born on January 20, 2024 belongs to the 癸卯 year (2023's stem-branch), not 甲辰 (2024's).

The library computes the exact 立春 moment using full VSOP87D planetary theory (2,425 terms) with DE405 correction and sxwnl-derived DeltaT.

子時 (Midnight Hour) crosses calendar days

子時 runs from 23:00 to 00:59, crossing the calendar midnight boundary. At 23:00+, the hour branch is 子 and the hour stem uses the next day's stem for the 甲己還加甲 rule. The day pillar itself does not advance until 00:00.

小寒 (Minor Cold) starts 丑月

The 12 month boundaries are defined by 節 (Jie) solar terms. 小寒 (~January 6) starts 丑月, and 立春 (~February 4) starts 寅月. Dates between 小寒 and 立春 belong to 丑月 of the previous stem-branch year.

Accuracy

Cross-validation against 寿星万年历 (sxwnl)

Validated against sxwnl, the gold standard Chinese calendar library by 許劍偉:

Test	Samples	Range	Result
Day Pillar (日柱)	5,683 dates	1583-2500	100% match
Year Pillar (年柱)	2,412 dates	1900-2100	100% match
Month Pillar (月柱)	2,412 dates	1900-2100	100% match
Solar Terms (節氣)	4,824 terms	1900-2100	avg 0.6s deviation
Lunar New Year (農曆)	61 dates	1990-2050	100% match
Intercalary Months (閏月)	10 years	2001-2025	100% match

Lunar calendar validated against Hong Kong Observatory / USNO data, including correct handling of the 二〇三三年問題 (2033 problem).

Solar term timing detail:

Percentile	Deviation
P50	0.5 seconds
P95	1.4 seconds
P99	2.0 seconds
Max	3.1 seconds
Within 1 min	100%

Full analysis with statistical charts: docs/accuracy.md

Data sources

Component	Source	Method
Solar longitude	VSOP87D	Full 2,425-term planetary theory + DE405 correction
New moon	Meeus Ch. 49	25 periodic + 14 planetary correction terms
Lunar calendar	Computed	冬至-anchor algorithm with zhongqi month numbering
Julian Day	Meeus Ch. 7	Julian/Gregorian calendar conversion
DeltaT (ΔT)	Espenak & Meeus + sxwnl	Polynomial (pre-2016), sxwnl cubic table (2016-2050), parabolic extrapolation (2050+)
Nutation	IAU2000B	77-term lunisolar nutation series
Equation of Time	Spencer 1971 Fourier	Accurate to ~30 seconds
Eclipse dates	NASA Five Millennium Canon	23,962 eclipses (-1999 to 3000 CE)
Day pillar	Arithmetic	Epoch: 2000-01-07 = 甲子日
Stem/branch cycles	Lookup tables	Standard 10-stem, 12-branch sequences

API Reference

1. Astronomical Foundations

DeltaT (ΔT)

Export	Description
`deltaT(date)`	ΔT in seconds for a Date (TT = UT + ΔT)
`deltaTForYear(y)`	ΔT in seconds for a decimal year

Julian Day Number (儒略日)

Export	Description
`julianDayNumber(year, month, day, calendar?)`	JD for a calendar date (Julian, Gregorian, or auto)
`jdToCalendarDate(jd, calendar?)`	Convert JD back to calendar date
`julianCalendarToDate(year, month, day)`	Convert a Julian calendar date to a JS Date

Solar Terms (節氣)

Export	Description
`SOLAR_TERM_NAMES`	24 term names (小寒 through 冬至)
`SOLAR_TERM_LONGITUDES`	Ecliptic longitudes (285° through 270°)
`findSolarTermMoment(longitude, year, startMonth?)`	Exact UTC moment for a solar longitude
`getSolarTermsForYear(year)`	All 24 terms with exact dates
`findSpringStart(year)`	Exact moment of 立春
`getSolarMonthExact(date)`	Which solar month a date falls in

New Moon (朔日)

Export	Description
`newMoonJDE(k)`	JDE of new moon for lunation number k (Meeus Ch. 49)
`findNewMoonsInRange(startJD, endJD)`	All new moon JDEs in a Julian Day range

Lunar Calendar (農曆)

Export	Description
`getLunarMonthsForYear(lunarYear)`	All lunar months for a year (12 or 13)
`getLunarNewYear(gregorianYear)`	Lunar New Year date (正月初一)
`gregorianToLunar(date)`	Convert Gregorian date to lunar date

Eclipses (日月食)

Export	Description
`getAllSolarEclipses()`	All solar eclipses (-1999 to 3000 CE), sorted by date
`getAllLunarEclipses()`	All lunar eclipses (-1999 to 3000 CE), sorted by date
`getEclipsesForYear(year)`	All eclipses for a given year
`getEclipsesInRange(start, end, kind?)`	Eclipses in a date range, optionally filtered
`findNearestEclipse(date, kind?)`	Nearest eclipse to a given date
`isEclipseDate(date)`	Check if a UTC date has an eclipse
`ECLIPSE_DATA_RANGE`	`{ min: -1999, max: 3000 }`

2. Stem-Branch System (干支)

Stems and Branches (天干地支)

Export	Description
`STEMS`	`['甲','乙','丙','丁','戊','己','庚','辛','壬','癸']`
`BRANCHES`	`['子','丑','寅','卯','辰','巳','午','未','申','酉','戌','亥']`
`STEM_ELEMENT`	`Record<Stem, Element>` (甲乙=木, 丙丁=火, ...)
`BRANCH_ELEMENT`	`Record<Branch, Element>`
`stemByIndex(n)`	Get stem by index (mod 10)
`branchByIndex(n)`	Get branch by index (mod 12)
`stemPolarity(stem)`	`'陽'` or `'陰'`
`branchPolarity(branch)`	`'陽'` or `'陰'`

Sexagenary Cycle (六十甲子)

Export	Description
`makeStemBranch(stem, branch)`	Build a `StemBranch` string
`stemBranchByCycleIndex(n)`	Get pair at position n in the 60-cycle
`stemBranchCycleIndex(stem, branch)`	Reverse lookup (returns -1 for invalid parity)
`parseStemBranch(str)`	Parse two-character string into stem + branch
`allSixtyStemBranch()`	All 60 valid pairs in cycle order

Five Elements (五行)

Export	Description
`GENERATIVE_CYCLE`	金→水→木→火→土→金
`CONQUERING_CYCLE`	金→木→土→水→火→金
`ELEMENT_ORDER`	`['金','木','水','火','土']`
`getElementRelation(from, to)`	Returns `'生'`, `'剋'`, `'被生'`, `'被剋'`, or `'比和'`

Cycle Elements (納音)

Export	Description
`CYCLE_ELEMENTS`	Full 60-pair lookup table with element and poetic name
`getCycleElement(sb)`	納音 element for a stem-branch pair
`getCycleElementName(sb)`	納音 poetic name (e.g. 海中金, 爐中火)

3. Pillar Relations (四柱八字)

Four Pillars (四柱)

Export	Description
`computeFourPillars(date)`	Compute year, month, day, and hour pillars

Hidden Stems (地支藏干)

Export	Description
`HIDDEN_STEMS`	`Record<Branch, HiddenStem[]>` — main, middle, residual stems
`getHiddenStems(branch)`	Hidden stems for a branch (main stem first)

Stem Relations (天干五合/相衝)

Export	Description
`STEM_COMBINATIONS`	Five stem combinations with transformed elements
`STEM_CLASHES`	Four stem clash pairs
`isStemCombination(a, b)`	Check if two stems form a 五合
`isStemClash(a, b)`	Check if two stems clash
`getCombinedElement(a, b)`	Transformed element of a combination, or null

Branch Relations (地支六合/六衝/三合/刑/害/破)

Export	Description
`HARMONY_PAIRS`	六合: 子丑, 寅亥, 卯戌, 辰酉, 巳申, 午未
`CLASH_PAIRS`	六衝: 子午, 丑未, 寅申, 卯酉, 辰戌, 巳亥
`THREE_HARMONIES`	三合: 申子辰水, 寅午戌火, 巳酉丑金, 亥卯未木
`SEASONAL_UNIONS`	三會: 寅卯辰木, 巳午未火, 申酉戌金, 亥子丑水
`HALF_HARMONIES`	半合: pairs from three-harmony groups
`PUNISHMENT_GROUPS`	刑: 寅巳申無恩, 丑戌未恃勢, 子卯無禮
`SELF_PUNISHMENT`	自刑: 辰午酉亥
`HARM_PAIRS`	六害: 子未, 丑午, 寅巳, 卯辰, 申亥, 酉戌
`DESTRUCTION_PAIRS`	六破: 子酉, 丑辰, 寅亥, 卯午, 巳申, 未戌
`isThreeHarmony(a, b, c)`	Check three-harmony group
`isPunishment(a, b)`	Check punishment relationship
`isSelfPunishment(branch)`	Check self-punishment
`isHarm(a, b)`	Check harm pair
`isDestruction(a, b)`	Check destruction pair

Hidden Harmony (暗合)

Export	Description
`HIDDEN_HARMONY_PAIRS`	Pre-computed pairs where main hidden stems form 五合
`isHiddenHarmony(a, b)`	Check if two branches have 暗合

Ten Relations (十神)

Export	Description
`TEN_RELATION_NAMES`	All 10 relation names
`getTenRelation(dayStem, otherStem)`	Derive the ten-relation
`getTenRelationForBranch(dayStem, branch)`	Ten-relation using main hidden stem

Twelve Life Stages (長生十二神)

Export	Description
`TWELVE_STAGES`	`['長生','沐浴','冠帶','臨官','帝旺','衰','病','死','墓','絕','胎','養']`
`getLifeStage(stem, branch)`	Life stage of a stem at a branch

Element Strength (旺相休囚死)

Export	Description
`STRENGTH`	`Record<Strength, string>` with descriptive labels
`getStrength(element, monthBranch)`	Seasonal strength: 旺, 相, 休, 囚, or 死

Earth Types (濕土/燥土)

Export	Description
`EARTH_BRANCHES`	`['辰','丑','戌','未']`
`isWetEarth(branch)`	辰丑 are wet earth
`isDryEarth(branch)`	戌未 are dry earth
`getStorageElement(branch)`	庫/墓: 辰→水, 戌→火, 丑→金, 未→木

Void Branches (旬空)

Export	Description
`computeVoidBranches(dayStem, dayBranch)`	`{ true: Branch, partial: Branch }` — 正空 (polarity match) and 偏空

Salary Star (祿神)

Export	Description
`SALARY_STAR`	`Record<Stem, Branch>` — stem → 臨官 branch
`getSalaryStar(stem)`	Get the 祿 branch for a stem

Virtue Stars (天德/月德)

Export	Description
`getMonthlyVirtue(monthBranch)`	月德: yang stem of the three-harmony element
`getHeavenlyVirtue(monthBranch)`	天德: traditional 12-entry lookup (stem or branch)
`getMonthlyVirtueCombo(monthBranch)`	月德合: 五合 partner of 月德
`getHeavenlyVirtueCombo(monthBranch)`	天德合: combination partner of 天德

Almanac Flags (神煞)

30 symbolic markers derived from stem-branch combinatorics:

Export	Description
`ALMANAC_FLAG_REGISTRY`	Full registry of all 30 flags with metadata
`getAlmanacFlags(date)`	All active flags for a date
`getAlmanacFlagsForPillars(pillars, season)`	All active flags from pre-computed pillars

Day stem derivations:

Export	Description
`getHeavenlyNoble(stem)`	天乙貴人: two noble branches
`getSupremeNoble(stem)`	太極貴人: supreme noble branches
`getLiteraryStar(stem)`	文昌貴人: literary star branch
`getProsperityStar(stem)`	祿神: prosperity branch
`getRamBlade(stem)`	羊刃: ram blade branch
`getGoldenCarriage(stem)`	金輿: golden carriage branch
`getStudyHall(stem)`	學堂: study hall (長生 position)

Branch derivations (三合 based):

Export	Description
`getTravelingHorse(branch)`	驛馬: from 三合 group
`getPeachBlossom(branch)`	桃花: from 三合 group
`getCanopy(branch)`	華蓋: from 三合 group
`getGeneralStar(branch)`	將星: from 三合 group
`getRobberyStar(branch)`	劫煞: from 三合 group
`getDeathSpirit(branch)`	亡神: from 三合 group

Branch derivations (other):

Export	Description
`getRedPhoenix(branch)`	紅鸞: red phoenix
`getHeavenlyJoy(branch)`	天喜: heavenly joy (紅鸞 + 6)
`getLonelyStar(branch)`	孤辰: lonely star
`getWidowStar(branch)`	寡宿: widow star
`getHeavenlyDoctor(branch)`	天醫: heavenly doctor (year branch + 1)

Day pillar predicates:

Export	Description
`isCommandingStar(stem, branch)`	魁罡: 庚辰/壬辰/庚戌/戊戌
`isTenEvils(stem, branch)`	十惡大敗: 10 specific day pillars
`isYinYangError(stem, branch)`	陰差陽錯: 12 specific day pillars
`isGoldSpirit(stem, branch)`	金神: 己巳/癸酉/乙丑
`isTenSpirits(stem, branch)`	十靈日: 10 specific day pillars
`isHeavenNet(branch)`	天羅: 戌/亥
`isEarthTrap(branch)`	地網: 辰/巳

Calendar predicates:

Export	Description
`isHeavensPardon(stem, branch, season)`	天赦日: seasonal pardon day
`isMonthBreak(dayBranch, monthBranch)`	月破: day clashes month
`isYearBreak(dayBranch, yearBranch)`	歲破: day clashes year
`isFourWaste(stem, branch, season)`	四廢: element dead in season

Multi-pillar patterns:

Export	Description
`getThreeWonders(pillars)`	三奇貴人: 乙丙丁 (天) / 甲戊庚 (地) / 壬癸辛 (人)

4. Eight-Character Derivations (八字推算)

Luck Periods (大運/小運)

Export	Description
`getLuckDirection(yearStem, gender)`	Yang+male or yin+female → forward; opposite → backward
`computeMajorLuck(birthDate, gender, count?)`	大運: 10-year periods from month pillar (default 8 periods)
`computeMinorLuck(hourPillar, direction, fromAge, toAge)`	小運: year-by-year pillars from hour pillar

5. Almanac Features (曆書)

Day Fitness (建除十二神)

Export	Description
`DAY_FITNESS_CYCLE`	`['建','除','滿','平','定','執','破','危','成','收','開','閉']`
`DAY_FITNESS_AUSPICIOUS`	Auspicious/inauspicious classification per fitness value
`getDayFitness(dayBranch, monthBranch)`	Fitness value from day and month branches
`getDayFitnessForDate(date)`	Fitness and auspicious flag for a date

Flying Stars (紫白九星)

Export	Description
`FLYING_STARS`	Nine stars: 一白 through 九紫 with element and color
`getYearStar(date)`	Year star (changes at 立春)
`getMonthStar(date)`	Month star (from year star group + solar month)
`getDayStar(date)`	Day star (continuous 9-day cycle)
`getHourStar(date)`	Hour star (from day star group + hour branch)
`getFlyingStars(date)`	All four stars (year, month, day, hour)

Peng Zu Taboos (彭祖百忌)

Export	Description
`getPengZuTaboo(stem, branch)`	Stem taboo + branch taboo strings
`getPengZuTabooForDate(date)`	Taboos for a date

Day Clash (沖煞)

Export	Description
`getDayClash(dayBranch)`	Clash branch + direction
`getDayClashForDate(date)`	Clash info for a date

Deity Directions (神煞方位)

Export	Description
`getDeityDirections(dayStem)`	喜神/福神/財神 directions from day stem
`getDeityDirectionsForDate(date)`	Directions for a date

Fetal Deity (胎神)

Export	Description
`getFetalDeity(stem, branch)`	胎神 location from day pillar
`getFetalDeityForDate(date)`	Fetal deity location for a date

Duty Deity (值神)

Export	Description
`DUTY_DEITIES`	The 12 duty deities in cycle order
`getDutyDeity(dayFitness, ...)`	Which deity is on duty
`getDutyDeityForDate(date)`	Duty deity for a date

Lunar Mansions (二十八星宿)

Export	Description
`LUNAR_MANSIONS`	28 mansions with luminary and element
`getLunarMansion(jd)`	Mansion from Julian Day (JD mod 28)
`getLunarMansionForDate(date)`	Mansion for a date

Chinese Zodiac (生肖)

Export	Description
`ZODIAC_ANIMALS`	`['鼠','牛','虎','兔','龍','蛇','馬','羊','猴','雞','狗','豬']`
`ZODIAC_ENGLISH`	`Record<ChineseZodiacAnimal, string>` (鼠→Rat, etc.)
`getChineseZodiac(date, boundary?)`	Zodiac with configurable year boundary (立春 or 初一)

Western Zodiac (星座)

Export	Description
`getWesternZodiac(date)`	Sign, symbol, Chinese name, Western element

True Solar Time (真太陽時)

Export	Description
`equationOfTime(date)`	EoT in minutes (Spencer 1971)
`trueSolarTime(clockTime, longitude, standardMeridian?)`	Corrected solar time with breakdown

6. Divination Systems (三式)

Six Ren (大六壬)

Export	Description
`STEM_LODGING`	日干寄宮: stem lodging branches
`HEAVENLY_GENERALS`	十二天將 in traditional order
`getMonthlyGeneral(date)`	月將: shifts at each 中氣 boundary
`buildPlates(monthlyGeneral, hourBranch)`	Build 天地盤 (heaven/earth plate rotation)
`buildFourLessons(dayStem, dayBranch, plates)`	Derive 四課 (four lessons)
`computeSixRen(dayStem, dayBranch, hourBranch, monthlyGeneral)`	Full chart from parameters
`computeSixRenForDate(date, hour?)`	Full chart for a date

Mystery Gates (奇門遁甲)

Export	Description
`NINE_STARS`	九星: 天蓬 through 天英
`EIGHT_DOORS`	八門: 休 through 開
`EIGHT_DEITIES`	八神: 值符 through 天禽
`SAN_QI_LIU_YI`	三奇六儀: 戊己庚辛壬癸丁丙乙
`getEscapeMode(date)`	陰遁 or 陽遁 for a date
`getJuShu(date)`	局數 (1-9) for a date
`buildEarthPlate(juShu)`	地盤: Lo Shu base layout
`buildHeavenPlate(earthPlate, ...)`	天盤: rotated overlay
`computeQiMen(...)`	Full chart from parameters
`computeQiMenForDate(date)`	Full chart for a date

Polaris Astrology (紫微斗數)

Export	Description
`MAJOR_STARS`	14 major stars (紫微 through 破軍)
`PALACE_NAMES`	12 palace names (命宮 through 父母宮)
`getFatepalace(lunarMonth, hourIndex)`	Fate palace branch index
`getElementPattern(fatePalaceIndex, yearStem)`	五行局 from 納音 (2-6)
`getZiWeiPosition(birthDay, elementPattern)`	紫微 star palace index
`computeZiWei(birthData)`	Full chart: 12 palaces, 14 stars, 四化, 流太歲

7. Composite

Daily Almanac (日曆總覽)

Export	Description
`dailyAlmanac(date)`	Complete almanac: pillars, lunar date, solar terms, zodiac, day fitness, flying stars, almanac flags, Six Ren, eclipses, element analysis

Types

type Stem = '甲' | '乙' | '丙' | '丁' | '戊' | '己' | '庚' | '辛' | '壬' | '癸';
type Branch = '子' | '丑' | '寅' | '卯' | '辰' | '巳' | '午' | '未' | '申' | '酉' | '戌' | '亥';
type StemBranch = `${Stem}${Branch}`;
type Element = '金' | '木' | '水' | '火' | '土';
type ElementRelation = '生' | '剋' | '被生' | '被剋' | '比和';
type Strength = '旺' | '相' | '休' | '囚' | '死';
type DayRelation = '生' | '剋' | '合' | '衝' | '比和';
type PunishmentType = '無恩' | '恃勢' | '無禮';
type EarthType = '濕' | '燥';
type TenRelation = '比肩' | '劫財' | '食神' | '傷官' | '偏財' | '正財' | '七殺' | '正官' | '偏印' | '正印';
type LifeStage = '長生' | '沐浴' | '冠帶' | '臨官' | '帝旺' | '衰' | '病' | '死' | '墓' | '絕' | '胎' | '養';
type DayFitness = '建' | '除' | '滿' | '平' | '定' | '執' | '破' | '危' | '成' | '收' | '開' | '閉';
type FlyingStar = 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9;
type AlmanacCategory = 'noble' | 'academic' | 'romance' | 'travel' | 'wealth' | 'protection' | 'health' | 'inauspicious';
type LuckDirection = 'forward' | 'backward';
type TransmissionMethod = '賊剋' | '比用' | '涉害' | '遙剋' | '昴星' | '別責' | '八專' | '返吟' | '伏吟';
type HeavenlyGeneral = '貴人' | '螣蛇' | '朱雀' | '六合' | '勾陳' | '青龍' | '天空' | '白虎' | '太常' | '玄武' | '太陰' | '天后';

interface Pillar { stem: Stem; branch: Branch; }
interface FourPillars { year: Pillar; month: Pillar; day: Pillar; hour: Pillar; }
interface HiddenStem { stem: Stem; proportion: number; }
interface SolarTerm { name: string; longitude: number; date: Date; }
interface LunarMonth { monthNumber: number; isLeapMonth: boolean; startDate: Date; days: number; }
interface LunarDate { year: number; month: number; day: number; isLeapMonth: boolean; }

interface MajorLuckPeriod { pillar: { stem: Stem; branch: Branch; stemBranch: StemBranch }; startAge: number; endAge: number; }
interface MajorLuckResult { direction: LuckDirection; startAge: number; periods: MajorLuckPeriod[]; }
interface MinorLuckYear { age: number; pillar: { stem: Stem; branch: Branch; stemBranch: StemBranch }; }

interface FlyingStarInfo { number: FlyingStar; name: string; element: Element; color: string; }
interface AlmanacFlagInfo { name: string; english: string; auspicious: boolean; category: AlmanacCategory; }
interface AlmanacFlagResult extends AlmanacFlagInfo { positions: ('year' | 'month' | 'day' | 'hour')[]; }

interface SixRenLesson { upper: Branch; lower: Branch; }
interface SixRenChart { dayStem: Stem; dayBranch: Branch; hourBranch: Branch; monthlyGeneral: Branch; plates: Record<Branch, Branch>; lessons: SixRenLesson[]; transmissions: { initial: Branch; middle: Branch; final: Branch }; method: TransmissionMethod; generals: Record<Branch, HeavenlyGeneral>; }

interface QiMenChart { earthPlate: Record<number, string>; heavenPlate: Record<number, string>; stars: Record<number, string>; doors: Record<number, string>; deities: Record<number, string>; escapeMode: string; juShu: number; zhiFu: { star: string; palace: number }; zhiShi: { door: string; palace: number }; }

interface ZiWeiBirthData { year: number; month: number; day: number; hour: number; gender: 'male' | 'female'; }
interface ZiWeiPalace { name: string; branch: Branch; stem: Stem; majorStars: string[]; }
interface SiHua { lu: string; quan: string; ke: string; ji: string; }
interface ZiWeiChart { palaces: ZiWeiPalace[]; elementPattern: number; siHua: SiHua; birthData: ZiWeiBirthData; fatePalaceIndex: number; bodyPalaceIndex: number; taiSuiIndex: number; }

type EclipseKind = 'solar' | 'lunar';
type SolarEclipseType = 'T' | 'A' | 'P' | 'H';
type LunarEclipseType = 'T' | 'P' | 'N';
interface Eclipse { date: Date; kind: EclipseKind; type: SolarEclipseType | LunarEclipseType; magnitude: number; }

Used By

stembranch-almanac — daily Chinese almanac with 三式合盤 (unified chart) showcasing all modules
iching4d — interactive I Ching explorer with 3D hexagram visualization

License

MIT

Name		Name	Last commit message	Last commit date
Latest commit History 46 Commits
almanac		almanac
data		data
docs		docs
src		src
tests		tests
.gitignore		.gitignore
LICENSE		LICENSE
README.md		README.md
package-lock.json		package-lock.json
package.json		package.json
tsconfig.json		tsconfig.json
tsup.config.ts		tsup.config.ts
vitest.config.ts		vitest.config.ts

Folders and files

Latest commit

History

Repository files navigation

stembranch

Install

Quickstart

Four Pillars (四柱八字)

Luck Periods (大運)

Daily Almanac (日曆總覽)

Divination Systems (三式)

Design Decisions

Year boundary: 立春 (Start of Spring), not January 1

子時 (Midnight Hour) crosses calendar days

小寒 (Minor Cold) starts 丑月

Accuracy

Cross-validation against 寿星万年历 (sxwnl)

Data sources

API Reference

1. Astronomical Foundations

DeltaT (ΔT)

Julian Day Number (儒略日)

Solar Terms (節氣)

New Moon (朔日)

Lunar Calendar (農曆)

Eclipses (日月食)

2. Stem-Branch System (干支)

Stems and Branches (天干地支)

Sexagenary Cycle (六十甲子)

Five Elements (五行)

Cycle Elements (納音)

3. Pillar Relations (四柱八字)

Four Pillars (四柱)

Hidden Stems (地支藏干)

Stem Relations (天干五合/相衝)

Branch Relations (地支六合/六衝/三合/刑/害/破)

Hidden Harmony (暗合)

Ten Relations (十神)

Twelve Life Stages (長生十二神)

Element Strength (旺相休囚死)

Earth Types (濕土/燥土)

Void Branches (旬空)

Salary Star (祿神)

Virtue Stars (天德/月德)

Almanac Flags (神煞)

4. Eight-Character Derivations (八字推算)

Luck Periods (大運/小運)

5. Almanac Features (曆書)

Day Fitness (建除十二神)

Flying Stars (紫白九星)

Peng Zu Taboos (彭祖百忌)

Day Clash (沖煞)

Deity Directions (神煞方位)

Fetal Deity (胎神)

Duty Deity (值神)

Lunar Mansions (二十八星宿)

Chinese Zodiac (生肖)

Western Zodiac (星座)

True Solar Time (真太陽時)

6. Divination Systems (三式)

Six Ren (大六壬)

Mystery Gates (奇門遁甲)

Polaris Astrology (紫微斗數)

7. Composite

Daily Almanac (日曆總覽)

Types

Used By

License

About

Topics

Resources

License

Uh oh!

Stars

Watchers

Forks

Releases

Packages 0

Uh oh!

Contributors

Packages