@gracefullight/saju

TypeScript library for calculating Four Pillars of Destiny (Saju, 四柱命理) with flexible date adapter support.

English | 한국어

Features

• Accurate Four Pillars Calculation - Implements traditional Chinese calendar algorithms with astronomical precision
• Flexible Date Adapter Pattern - Use Luxon, date-fns, or bring your own date library
• Timezone & Location Support - Proper handling of timezones and geographic coordinates
• Solar Time Correction - Optional mean solar time adjustment based on longitude
• Tree-shakeable - Import only what you need
• Fully Typed - Complete TypeScript definitions
• Well Tested - 180+ tests with 91%+ coverage
• Ten Gods Analysis - Detailed ten gods and five elements distribution with hidden stems
• Strength Assessment - 9-level strength analysis with monthly strength (得令), root strength (通根), transparency (透干), and hidden stem weights (本中餘氣)
• Relations Analysis - Combinations, clashes, harms, punishments with transformation (化) status and conditions
• Major/Yearly Luck - Solar term (節氣) based accurate luck start calculation, major luck and yearly luck based on gender and year pillar
• Yongshen Extraction - Favorable element recommendation following 格局→抑扶→調候 priority with fortune enhancement guide
• Solar Terms Analysis - Current/next solar term info with elapsed days calculation

What is Saju (四柱)?

Saju (Four Pillars of Destiny, 四柱命理) is a traditional Korean and Chinese divination system based on one's birth year, month, day, and hour. Each pillar consists of:

• Heavenly Stem (天干): 10 elements (甲乙丙丁戊己庚辛壬癸)
• Earthly Branch (地支): 12 zodiac signs (子丑寅卯辰巳午未申酉戌亥)

This library calculates these pillars using:

• Lichun (立春, Start of Spring) for year pillar transitions
• Solar longitude for month pillar determination
• Julian Day Number for day pillar calculation
• Traditional Chinese double-hour system (時辰, shichen) for hour pillar

Installation

# Using pnpm
pnpm add @gracefullight/saju

# Using npm
npm install @gracefullight/saju

# Using yarn
yarn add @gracefullight/saju

Date Library Adapters

Choose one based on your preference:

# Option 1: Luxon (recommended for modern apps)
pnpm add luxon @types/luxon

# Option 2: date-fns (lightweight alternative)
pnpm add date-fns date-fns-tz

Quick Start

import { DateTime } from "luxon";
import { createLuxonAdapter } from "@gracefullight/saju/adapters/luxon";
import { getSaju } from "@gracefullight/saju";

const adapter = await createLuxonAdapter();

const birthDateTime = DateTime.fromObject(
  { year: 2000, month: 1, day: 1, hour: 18, minute: 0 },
  { zone: "Asia/Seoul" }
);

// getSaju: Calculate pillars, ten gods, strength, relations, yongshen, solar terms, major luck, yearly luck all at once
const result = getSaju(birthDateTime, {
  adapter,
  gender: "male",  // Required: needed for major luck calculation
  // longitudeDeg: 126.9778,  // Optional: uses timezone-based longitude if omitted
  // preset: STANDARD_PRESET, // Optional: defaults to STANDARD_PRESET
  // yearlyLuckRange: { from: 2024, to: 2030 },  // Optional: specify yearly luck range
});

console.log(result.pillars);     // { year: "己卯", month: "丙子", ... }
console.log(result.tenGods);     // Ten gods and hidden stems analysis
console.log(result.strength);    // Strength assessment (e.g., "weak")
console.log(result.relations);   // Relations analysis
console.log(result.yongShen);    // Yongshen and fortune tips
console.log(result.solarTerms);  // Solar term info (current/next term, elapsed days)
console.log(result.majorLuck);   // Major luck info
console.log(result.yearlyLuck);  // Yearly luck info

Calculate Four Pillars Only

import { DateTime } from "luxon";
import { createLuxonAdapter } from "@gracefullight/saju/adapters/luxon";
import { getFourPillars } from "@gracefullight/saju";

const adapter = await createLuxonAdapter();

const birthDateTime = DateTime.fromObject(
  { year: 2000, month: 1, day: 1, hour: 18, minute: 0 },
  { zone: "Asia/Seoul" }
);

const result = getFourPillars(birthDateTime, { adapter });

console.log(result);

Usage

With Luxon

import { DateTime } from "luxon";
import { createLuxonAdapter } from "@gracefullight/saju/adapters/luxon";
import { getFourPillars, STANDARD_PRESET, TRADITIONAL_PRESET } from "@gracefullight/saju";

const adapter = await createLuxonAdapter();

const dt = DateTime.fromObject(
  { year: 2000, month: 1, day: 1, hour: 18, minute: 0 },
  { zone: "Asia/Seoul" }
);

// Standard Preset: Midnight (00:00) day boundary, no solar time correction
const resultStandard = getFourPillars(dt, {
  adapter,
  longitudeDeg: 126.9778,
  preset: STANDARD_PRESET,
});

// Traditional Preset: Zi hour (23:00) day boundary, with solar time correction
const resultTraditional = getFourPillars(dt, {
  adapter,
  longitudeDeg: 126.9778,
  preset: TRADITIONAL_PRESET,
});

With date-fns

import { createDateFnsAdapter } from "@gracefullight/saju/adapters/date-fns";
import { getFourPillars, STANDARD_PRESET } from "@gracefullight/saju";

const adapter = await createDateFnsAdapter();

const dt = {
  date: new Date(1985, 4, 15, 14, 30), // Note: month is 0-indexed
  timeZone: "Asia/Seoul",
};

const result = getFourPillars(dt, {
  adapter,
  longitudeDeg: 126.9778,
  preset: STANDARD_PRESET,
});

Custom Date Adapter

Implement the DateAdapter interface to use any date library:

import type { DateAdapter } from "@gracefullight/saju";

const myAdapter: DateAdapter<MyDateType> = {
  // Date component getters
  getYear: (date) => date.year,
  getMonth: (date) => date.month,
  getDay: (date) => date.day,
  getHour: (date) => date.hour,
  getMinute: (date) => date.minute,
  getSecond: (date) => date.second,
  getZoneName: (date) => date.zoneName,

  // Date arithmetic
  plusMinutes: (date, minutes) => date.add({ minutes }),
  plusDays: (date, days) => date.add({ days }),
  minusDays: (date, days) => date.subtract({ days }),

  // Timezone operations
  toUTC: (date) => date.toUTC(),
  setZone: (date, zoneName) => date.setZone(zoneName),

  // Conversions
  toISO: (date) => date.toISO(),
  toMillis: (date) => date.valueOf(),
  fromMillis: (millis, zone) => MyDate.fromMillis(millis, zone),

  // Utilities
  createUTC: (year, month, day, hour, minute, second) =>
    MyDate.utc(year, month, day, hour, minute, second),
  isGreaterThanOrEqual: (date1, date2) => date1 >= date2,
};

API Reference

Configuration Presets

STANDARD_PRESET

Contemporary interpretation with midnight day boundary and no solar time correction.

{
  dayBoundary: "midnight",           // Day starts at 00:00
  useMeanSolarTimeForHour: false,    // Use local time for hour
  useMeanSolarTimeForBoundary: false // Use local time for day boundary
}

TRADITIONAL_PRESET

Traditional interpretation with Zi hour (23:00) day boundary and solar time correction.

{
  dayBoundary: "zi23",               // Day starts at 23:00 (子時)
  useMeanSolarTimeForHour: true,     // Use solar time for hour
  useMeanSolarTimeForBoundary: true  // Use solar time for day boundary
}

Core Functions

getSaju(datetime, options)

Calculate all saju analysis results (pillars, ten gods, strength, relations, yongshen, solar terms, major luck, yearly luck) at once.

function getSaju<T>(
  dtLocal: T,
  options: {
    adapter: DateAdapter<T>;
    longitudeDeg?: number;
    gender: "male" | "female";  // Required
    tzOffsetHours?: number;
    preset?: typeof STANDARD_PRESET;
    currentYear?: number;  // For default yearly luck range
    yearlyLuckRange?: { from: number; to: number };  // Specify yearly luck range directly
  }
): SajuResult;

getFourPillars(datetime, options)

Calculate all four pillars (year, month, day, hour).

function getFourPillars<T>(
  datetime: T,
  options: {
    adapter: DateAdapter<T>;
    longitudeDeg?: number;
    preset?: {
      dayBoundary: "midnight" | "zi23";
      useMeanSolarTimeForHour: boolean;
      useMeanSolarTimeForBoundary: boolean;
    };
    tzOffsetHours?: number;
  }
): {
  year: string;
  month: string;
  day: string;
  hour: string;
  lunar: {
    lunarYear: number;
    lunarMonth: number;
    lunarDay: number;
    isLeapMonth: boolean;
  };
  meta: {
    solarYearUsed: number;
    sunLonDeg: number;
    effectiveDayDate: { year: number; month: number; day: number };
    adjustedDtForHour: string;
  };
}

Parameters:

• datetime: Date/time object in the adapter's format
• options:
  • adapter: DateAdapter instance
  • longitudeDeg: Geographic longitude in degrees (e.g., Seoul: 126.9778), optional
  • preset: Configuration preset (use STANDARD_PRESET or TRADITIONAL_PRESET)
  • tzOffsetHours: Optional timezone offset in hours (default: 9 for KST)

Returns: Object with year, month, day, hour pillars, lunar date, and metadata

yearPillar(datetime, options)

Calculate only the year pillar based on Lichun (立春, Start of Spring).

function yearPillar<T>(
  datetime: T,
  options: { adapter: DateAdapter<T> }
): {
  idx60: number;
  pillar: string;
  solarYear: number;
}

monthPillar(datetime, options)

Calculate only the month pillar based on solar longitude.

function monthPillar<T>(
  datetime: T,
  options: { adapter: DateAdapter<T> }
): {
  pillar: string;
  sunLonDeg: number;
}

dayPillarFromDate({ year, month, day })

Calculate only the day pillar using Julian Day Number.

function dayPillarFromDate(date: {
  year: number;
  month: number;
  day: number;
}): {
  idx60: number;
  pillar: string;
}

Lunar Conversion Functions

getLunarDate(year, month, day)

Convert a solar (Gregorian) date to a lunar date.

function getLunarDate(
  year: number,
  month: number,
  day: number
): {
  lunarYear: number;
  lunarMonth: number;
  lunarDay: number;
  isLeapMonth: boolean;
}

Example:

import { getLunarDate } from "@gracefullight/saju";

const lunar = getLunarDate(2000, 1, 1);
// { lunarYear: 1999, lunarMonth: 11, lunarDay: 25, isLeapMonth: false }

getSolarDate(lunarYear, lunarMonth, lunarDay, isLeapMonth)

Convert a lunar date to a solar (Gregorian) date.

function getSolarDate(
  lunarYear: number,
  lunarMonth: number,
  lunarDay: number,
  isLeapMonth?: boolean
): {
  year: number;
  month: number;
  day: number;
}

Example:

import { getSolarDate } from "@gracefullight/saju";

const solar = getSolarDate(1999, 11, 25, false);
// { year: 2000, month: 1, day: 1 }

hourPillar(datetime, options)

Calculate only the hour pillar with optional solar time correction.

function hourPillar<T>(
  datetime: T,
  options: {
    adapter: DateAdapter<T>;
    longitudeDeg?: number;
    tzOffsetHours?: number;
    useMeanSolarTimeForHour?: boolean;
    dayBoundary?: "midnight" | "zi23";
    useMeanSolarTimeForBoundary?: boolean;
  }
): {
  pillar: string;
  adjustedDt: T;
  adjustedHour: number;
}

Constants

// 10 Heavenly Stems (天干)
export const STEMS: string[];
// ["甲", "乙", "丙", "丁", "戊", "己", "庚", "辛", "壬", "癸"]

// 12 Earthly Branches (地支)
export const BRANCHES: string[];
// ["子", "丑", "寅", "卯", "辰", "巳", "午", "未", "申", "酉", "戌", "亥"]

Helper Functions

applyMeanSolarTime(adapter, dtLocal, longitudeDeg, tzOffsetHours)

Apply mean solar time correction based on longitude.

function applyMeanSolarTime<T>(
  adapter: DateAdapter<T>,
  dtLocal: T,
  longitudeDeg: number,
  tzOffsetHours: number
): T

effectiveDayDate(dtLocal, options)

Calculate the effective date considering day boundary rules.

function effectiveDayDate<T>(
  dtLocal: T,
  options: {
    adapter: DateAdapter<T>;
    dayBoundary?: "midnight" | "zi23";
    longitudeDeg?: number;
    tzOffsetHours?: number;
    useMeanSolarTimeForBoundary?: boolean;
  }
): {
  year: number;
  month: number;
  day: number;
}

Analysis Functions

analyzeTenGods(year, month, day, hour)

Analyzes ten gods and hidden stems of the four pillars.

function analyzeTenGods(
  year: string,
  month: string,
  day: string,
  hour: string
): FourPillarsTenGods;

analyzeStrength(year, month, day, hour)

Assesses the strength of the day master on a 7-level scale.

function analyzeStrength(
  year: string,
  month: string,
  day: string,
  hour: string
): StrengthResult;

analyzeRelations(year, month, day, hour)

Analyzes combinations, clashes, harms, and punishments between stems and branches.

function analyzeRelations(
  year: string,
  month: string,
  day: string,
  hour: string
): RelationsResult;

calculateMajorLuck(birthDateTime, gender, yearPillar, monthPillar, options)

Calculates major luck periods and starting age.

function calculateMajorLuck<T>(
  birthDateTime: T,
  gender: "male" | "female",
  yearPillar: string,
  monthPillar: string,
  options: { adapter: DateAdapter<T>; longitudeDeg?: number; tzOffsetHours?: number }
): MajorLuckResult;

analyzeYongShen(year, month, day, hour)

Extracts favorable elements considering suppression and climate adjustment.

function analyzeYongShen(
  year: string,
  month: string,
  day: string,
  hour: string
): YongShenResult;

analyzeSolarTerms(datetime, options)

Calculates current and next solar term info with elapsed days.

function analyzeSolarTerms<T>(
  dtLocal: T,
  options: { adapter: DateAdapter<T> }
): SolarTermInfo;

Returns:

{
  current: { name: "소한", hanja: "小寒", longitude: 285 },
  currentDate: { year: 2024, month: 1, day: 6, hour: 5, minute: 30 },
  daysSinceCurrent: 5,
  next: { name: "대한", hanja: "大寒", longitude: 300 },
  nextDate: { year: 2024, month: 1, day: 20, hour: 12, minute: 15 },
  daysUntilNext: 10
}

getSolarTermsForYear(year, options)

Calculates all 24 solar terms for a specific year.

function getSolarTermsForYear<T>(
  year: number,
  options: { adapter: DateAdapter<T>; timezone: string }
): Array<{ term: SolarTerm; date: {...} }>;

Advanced Usage

Solar Time Correction

Solar time correction adjusts local time based on longitude to account for the difference between local clock time and actual solar time.

import { applyMeanSolarTime, createLuxonAdapter } from "@gracefullight/saju";
import { DateTime } from "luxon";

const adapter = await createLuxonAdapter();
const localTime = DateTime.local(2024, 1, 1, 12, 0, 0, { zone: "Asia/Seoul" });

// Seoul is at 126.9778°E, but uses UTC+9 (135°E standard meridian)
// This creates a ~32 minute difference
const solarTime = applyMeanSolarTime(adapter, localTime, 126.9778, 9);
console.log(solarTime.hour); // ~11.47 (11:28)

Day Boundary Modes

Midnight Mode (dayBoundary: "midnight"):

• Day changes at 00:00 local time
• Simpler, aligns with contemporary calendar systems
• Suitable for general use

Zi Hour Mode (dayBoundary: "zi23"):

• Day changes at 23:00 local time
• Traditional Chinese timekeeping
• Zi hour (子時) straddles midnight (23:00-01:00)

const result1 = getFourPillars(dt, {
  adapter,
  longitudeDeg: 126.9778,
  preset: { ...STANDARD_PRESET, dayBoundary: "midnight" },
});

const result2 = getFourPillars(dt, {
  adapter,
  longitudeDeg: 126.9778,
  preset: { ...STANDARD_PRESET, dayBoundary: "zi23" },
});

Custom Configuration

Mix and match settings for specific needs:

const customConfig = {
  dayBoundary: "midnight" as const,      // Contemporary midnight boundary
  useMeanSolarTimeForHour: true,         // But use solar time for hour
  useMeanSolarTimeForBoundary: false,    // Local time for day boundary
};

const result = getFourPillars(dt, {
  adapter,
  longitudeDeg: 126.9778,
  preset: customConfig,
});

Geographic Coordinates

Common city longitudes for reference:

| City | Longitude | Example | |------|-----------|---------| | Seoul, South Korea | 126.9778°E | longitudeDeg: 126.9778 | | Beijing, China | 116.4074°E | longitudeDeg: 116.4074 | | Tokyo, Japan | 139.6917°E | longitudeDeg: 139.6917 | | Shanghai, China | 121.4737°E | longitudeDeg: 121.4737 | | Taipei, Taiwan | 121.5654°E | longitudeDeg: 121.5654 |

Examples

Major and Yearly Luck Calculation

const saju = getSaju(dt, {
  adapter,
  longitudeDeg: 126.9778,
  gender: "female",
  yearlyLuckRange: { from: 2024, to: 2030 }
});

// Check major luck
console.log(saju.majorLuck.pillars); // Major luck pillars list
console.log(saju.majorLuck.startAge); // Starting age for major luck

// Check yearly luck
saju.yearlyLuck.forEach(luck => {
  console.log(`Year ${luck.year} (${luck.pillar}): Age ${luck.age}`);
});

Solar Terms Info

const saju = getSaju(dt, {
  adapter,
  longitudeDeg: 126.9778,
  gender: "male",
});

// Current solar term
console.log(saju.solarTerms.current.name);  // "소한"
console.log(saju.solarTerms.current.hanja); // "小寒"
console.log(saju.solarTerms.daysSinceCurrent); // 5 (days since term started)

// Next solar term
console.log(saju.solarTerms.next.name);     // "대한"
console.log(saju.solarTerms.daysUntilNext); // 10 (days until next term)

// Solar term dates
console.log(saju.solarTerms.currentDate);   // { year: 2024, month: 1, day: 6, ... }
console.log(saju.solarTerms.nextDate);      // { year: 2024, month: 1, day: 20, ... }

Ten Gods and Five Elements Analysis

import { analyzeTenGods, countElements } from "@gracefullight/saju";

const tenGods = analyzeTenGods("己卯", "丙子", "辛巳", "戊戌");
console.log(tenGods.dayMaster); // "辛"

const elements = countElements(tenGods);
console.log(elements); // { wood: 1, fire: 1, earth: 3, metal: 1, water: 2 }

Strength and Yongshen Analysis

import { analyzeStrength, analyzeYongShen, getElementRecommendations } from "@gracefullight/saju";

const strength = analyzeStrength("己卯", "丙子", "辛巳", "戊戌");
console.log(strength.level); // "weak"

const yongShen = analyzeYongShen("己卯", "丙子", "辛巳", "戊戌");
console.log(yongShen.primary); // Favorable element (e.g., "earth")

const tips = getElementRecommendations(yongShen);
console.log(tips.colors); // Lucky colors

Relations Analysis

import { analyzeRelations } from "@gracefullight/saju";

const relations = analyzeRelations("己卯", "丙子", "辛巳", "戊戌");
relations.clashes.forEach(c => {
  console.log(`${c.positions[0]}-${c.positions[1]} branch clash: ${c.pair[0]}-${c.pair[1]}`);
});

Calculate for Different Timezones

import { DateTime } from "luxon";
import { createLuxonAdapter, getFourPillars, TRADITIONAL_PRESET } from "@gracefullight/saju";

const adapter = await createLuxonAdapter();

// New York birth time
const nyTime = DateTime.fromObject(
  { year: 1985, month: 5, day: 15, hour: 6, minute: 30 },
  { zone: "America/New_York" }
);

const result = getFourPillars(nyTime, {
  adapter,
  longitudeDeg: -74.0060, // NYC longitude
  tzOffsetHours: -5,      // EST offset
  preset: TRADITIONAL_PRESET,
});

Calculate Individual Pillars

import { yearPillar, monthPillar, dayPillarFromDate, hourPillar } from "@gracefullight/saju";

// Year pillar
const year = yearPillar(dt, { adapter });
console.log(year.pillar, year.solarYear);

// Month pillar
const month = monthPillar(dt, { adapter });
console.log(month.pillar, month.sunLonDeg);

// Day pillar (no adapter needed)
const day = dayPillarFromDate({ year: 1985, month: 5, day: 15 });
console.log(day.pillar);

// Hour pillar with solar time
const hour = hourPillar(dt, {
  adapter,
  longitudeDeg: 126.9778,
  useMeanSolarTimeForHour: true,
});
console.log(hour.pillar, hour.adjustedHour);

Batch Processing

const birthDates = [
  { year: 1990, month: 1, day: 15, hour: 10, minute: 30 },
  { year: 1995, month: 5, day: 20, hour: 14, minute: 45 },
  { year: 2000, month: 12, day: 25, hour: 18, minute: 0 },
];

const adapter = await createLuxonAdapter();

const results = birthDates.map((birth) => {
  const dt = DateTime.fromObject(birth, { zone: "Asia/Seoul" });
  return {
    birth,
    pillars: getFourPillars(dt, {
      adapter,
      longitudeDeg: 126.9778,
      preset: STANDARD_PRESET,
    }),
  };
});

Development

Setup

# Clone repository
git clone https://github.com/gracefullight/saju.git
cd saju

# Install dependencies
pnpm install

# Run tests
pnpm test

# Run tests with coverage
pnpm test:coverage

# Build
pnpm build

# Lint
pnpm lint

# Format
pnpm lint:fix

Project Structure

packages/saju/
├── src/
│   ├── adapters/           # Date library adapters
│   │   ├── date-adapter.ts # Adapter interface
│   │   ├── luxon.ts        # Luxon adapter
│   │   └── date-fns.ts     # date-fns adapter
│   ├── core/               # Core calculation logic
│   │   ├── four-pillars.ts # Four pillars calculation
│   │   ├── ten-gods.ts     # Ten gods analysis
│   │   ├── strength.ts     # Strength assessment
│   │   ├── relations.ts    # Relations analysis
│   │   ├── luck.ts         # Major/yearly luck
│   │   ├── yongshen.ts     # Yongshen extraction
│   │   ├── solar-terms.ts  # Solar terms calculation
│   │   └── lunar.ts        # Lunar conversion
│   ├── types/              # Type definitions
│   ├── __tests__/          # Test suites
│   └── index.ts            # Public API
├── dist/                   # Compiled output
├── coverage/               # Test coverage reports
└── README.md

Running Tests

# Run all tests
pnpm test

# Run tests in watch mode
pnpm test:watch

# Generate coverage report
pnpm test:coverage

Coverage results:

File               | % Stmts | % Branch | % Funcs | % Lines
-------------------|---------|----------|---------|----------
All files          |   91.45 |    80.68 |   96.55 |   91.45
 src/adapters      |   94.59 |    90.24 |     100 |   94.59
 src/core          |   96.87 |    75.55 |     100 |   96.87

FAQ

Why use date adapters instead of a single date library?

Different projects use different date libraries. The adapter pattern allows you to:

• Use your existing date library without adding another dependency
• Keep bundle size minimal by only including what you need
• Maintain consistency with your project's date handling

What's the difference between STANDARD_PRESET and TRADITIONAL_PRESET?

STANDARD_PRESET uses contemporary conventions:

• Day starts at midnight (00:00)
• Uses local clock time
• Simpler for general use

TRADITIONAL_PRESET follows traditional Chinese astrology practices:

• Day starts at Zi hour (23:00)
• Applies solar time correction based on longitude
• More historically accurate

How accurate are the calculations?

The library implements:

• Julian Day Number algorithm for day pillars (accurate across all historical dates)
• Astronomical solar longitude calculations for month pillars
• Lichun (Start of Spring) calculation for year pillars
• Traditional Chinese hour system (時辰) for hour pillars

All algorithms are tested with known historical dates and match traditional Chinese calendar references.

Can I use this for historical dates?

Yes! The Julian Day Number algorithm works correctly for:

• All dates in the Gregorian calendar (1582 onwards)
• Most dates in the Julian calendar (with appropriate calendar conversion)
• Dates far in the future

However, note that timezone data may be less accurate for dates before ~1970.

Why does the same birth time give different results with different presets?

The presets affect:

1. Day boundary: When the day actually changes (midnight vs. 23:00)
2. Solar time: Whether to adjust for longitude difference

For example, 23:30 could be:

• Same day's Zi hour (with midnight boundary)
• Next day's Zi hour (with Zi23 boundary)

This is intentional and reflects different interpretative traditions in Saju analysis.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

Guidelines

• Write tests for new features
• Maintain or improve code coverage
• Follow existing code style (enforced by Biome)
• Update documentation as needed

License

MIT © gracefullight

Credits

This library is based on traditional Chinese calendar algorithms and astronomical calculations used in Four Pillars astrology (四柱命理).

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