Compass AI Bazi

Chinese Bazi (八字) four-pillar fortune calculation and basic interpretation — enables AI agents to compute and read a birth chart using traditional Zi-Ping methodology.

Compass AI — Bazi (八字) Calculation & Lite Interpretation

This skill gives you the complete reference data and step-by-step algorithms needed to calculate a Chinese Bazi (Four Pillars of Destiny) chart from a person's birth date, time, and location, and to produce a basic personality and fortune interpretation.

⚠️ NO EXTERNAL TOOLS OR LIBRARIES NEEDED. Every calculation in this skill — year pillar, month pillar, day pillar, hour pillar, Ten Gods, Five Elements, Major Fortune Cycles — is performed by you, the AI, using only arithmetic and the lookup tables below. Do NOT attempt to call any tool, install any library, or search the web. Just reason through the steps.

For full AI-powered streaming analysis, life K-line charts, two-person compatibility, daily fortune sticks, and interactive fortune-telling chat, visit Compass AI.

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When to Use This Skill

Use this skill when the user:

• Provides a birth date, birth time, and birth city/location and asks for a Bazi (八字) reading
• Asks about their Four Pillars, Day Master, Five Elements balance, Ten Gods, or Major Fortune cycles
• Wants to know their favorable/unfavorable elements (喜用神/忌神)
• Asks about personality traits or career tendencies based on Chinese astrology

Important UX rules:

• Only ask the user for: birth date (年月日), birth time (时辰), gender, and birth city name. Never ask for longitude/latitude — look it up from the City Coordinates table below.
• If the city is not in the table, estimate from the nearest listed city or provincial capital.
• Collect all info in as few turns as possible. Ideally one message: "请告诉我您的出生年月日、时辰、性别和出生城市".

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Core Concepts (Quick Reference)

Heavenly Stems (天干) and Their Five Elements

Stem	Pinyin	Element	Polarity
甲	jiǎ	木 Wood	Yang
乙	yǐ	木 Wood	Yin
丙	bǐng	火 Fire	Yang
丁	dīng	火 Fire	Yin
戊	wù	土 Earth	Yang
己	jǐ	土 Earth	Yin
庚	gēng	金 Metal	Yang
辛	xīn	金 Metal	Yin
壬	rén	水 Water	Yang
癸	guǐ	水 Water	Yin

Earthly Branches (地支) and Their Five Elements

Branch	Pinyin	Element	Zodiac
子	zǐ	水 Water	Rat
丑	chǒu	土 Earth	Ox
寅	yín	木 Wood	Tiger
卯	mǎo	木 Wood	Rabbit
辰	chén	土 Earth	Dragon
巳	sì	火 Fire	Snake
午	wǔ	火 Fire	Horse
未	wèi	土 Earth	Goat
申	shēn	金 Metal	Monkey
酉	yǒu	金 Metal	Rooster
戌	xū	土 Earth	Dog
亥	hài	水 Water	Pig

Five Elements Generating & Controlling Cycles (五行生克)

Generating (相生): Wood → Fire → Earth → Metal → Water → Wood

Controlling (相克): Wood → Earth → Water → Fire → Metal → Wood

Hidden Stems in Earthly Branches (地支藏干)

Each Earthly Branch contains one or more hidden Heavenly Stems with relative strength weights (main qi / middle qi / residual qi):

Branch	Main Qi (本气)	Middle Qi (中气)	Residual Qi (余气)
子	癸 (100%)	—	—
丑	己 (60%)	癸 (30%)	辛 (10%)
寅	甲 (60%)	丙 (30%)	戊 (10%)
卯	乙 (100%)	—	—
辰	戊 (60%)	乙 (30%)	癸 (10%)
巳	丙 (60%)	戊 (30%)	庚 (10%)
午	丁 (70%)	己 (30%)	—
未	己 (60%)	丁 (30%)	乙 (10%)
申	庚 (60%)	壬 (30%)	戊 (10%)
酉	辛 (100%)	—	—
戌	戊 (60%)	辛 (30%)	丁 (10%)
亥	壬 (70%)	甲 (30%)	—

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City Coordinates Lookup (城市经纬度)

When the user provides a birth city, resolve it to longitude (lng) and latitude (lat) using this table. Do NOT ask the user for coordinates -- look them up here automatically.

If the city is not listed, estimate from a nearby city or use a reasonable default (e.g. provincial capital).

China — Municipalities & Provincial Capitals

City	lng	lat
北京	116.407	39.904
上海	121.474	31.230
天津	117.201	39.084
重庆	106.552	29.563
南京	118.797	32.060
杭州	120.155	30.274
广州	113.264	23.129
深圳	114.058	22.543
成都	104.067	30.573
武汉	114.316	30.581
西安	108.940	34.342
郑州	113.640	34.757
济南	117.121	36.652
沈阳	123.432	41.806
长春	125.324	43.817
哈尔滨	126.536	45.802
石家庄	114.515	38.043
太原	112.549	37.871
呼和浩特	111.752	40.841
合肥	117.227	31.821
福州	119.297	26.075
南昌	115.892	28.677
长沙	112.939	28.228
海口	110.331	20.022
昆明	102.715	25.049
贵阳	106.630	26.648
拉萨	91.141	29.646
兰州	103.834	36.061
西宁	101.778	36.617
银川	106.231	38.487
乌鲁木齐	87.617	43.826
南宁	108.367	22.817

China — Other Major Cities

City	lng	lat
苏州	120.585	31.299
无锡	120.312	31.491
宁波	121.544	29.868
温州	120.699	28.001
厦门	118.111	24.480
青岛	120.383	36.067
大连	121.615	38.914
烟台	121.391	37.539
珠海	113.577	22.271
佛山	113.121	23.022
东莞	113.752	23.021
桂林	110.290	25.274
洛阳	112.454	34.620
开封	114.308	34.797
保定	115.465	38.874
唐山	118.180	39.631
大同	113.300	40.077
包头	109.840	40.657
齐齐哈尔	123.918	47.354
大庆	125.103	46.589

International Cities

City	lng	lat
纽约	-74.006	40.713
洛杉矶	-118.244	34.052
旧金山	-122.419	37.775
芝加哥	-87.630	41.878
西雅图	-122.332	47.606
波士顿	-71.059	42.360
华盛顿	-77.037	38.907
伦敦	-0.128	51.507
巴黎	2.352	48.857
柏林	13.405	52.520
莫斯科	37.617	55.756
东京	139.650	35.676
大阪	135.502	34.694
首尔	126.978	37.567
新加坡	103.820	1.352
曼谷	100.502	13.756
悉尼	151.209	-33.869
墨尔本	144.963	-37.814
多伦多	-79.383	43.653
温哥华	-123.122	49.283

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Calculation Steps

Reminder: Perform all steps below yourself using arithmetic. Do not call any tool or library.

Step 1: True Solar Time Conversion

Standard Chinese time is based on Beijing (120°E). Adjust for the birth location:

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time_offset_minutes = (birth_longitude - 120.0) × 4
true_solar_time = local_time + time_offset_minutes

Step 2: Four Pillars (四柱) — Direct Arithmetic (No Library)

All four pillars are computed with arithmetic and lookup tables. Work through each sub-step in order.

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2a. Year Pillar (年柱)

Use the birth year (if the birth date is before 立春 of that year, use the previous year):

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year_stem_index   = (year − 4) % 10   → index into Stems list (甲=0 … 癸=9)
year_branch_index = (year − 4) % 12   → index into Branches list (子=0 … 亥=11)

Example: 1990 → stem = (1990−4)%10 = 6 → 庚 ; branch = (1990−4)%12 = 6 → 午 → 庚午年

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2b. Month Pillar (月柱)

The Bazi month changes at solar terms (节令), NOT at the lunar new month. Find which month the true-solar-time date falls in using the table below, then derive the stem.

Month Branch by Solar Term:

Bazi Month	Branch	Solar Term (节)	Approx. Start
1	寅	立春 Start of Spring	Feb 4
2	卯	惊蛰 Awakening of Insects	Mar 6
3	辰	清明 Clear and Bright	Apr 5
4	巳	立夏 Start of Summer	May 6
5	午	芒种 Grain in Ear	Jun 6
6	未	小暑 Minor Heat	Jul 7
7	申	立秋 Start of Autumn	Aug 7
8	酉	白露 White Dew	Sep 8
9	戌	寒露 Cold Dew	Oct 8
10	亥	立冬 Start of Winter	Nov 7
11	子	大雪 Major Snow	Dec 7
12	丑	小寒 Minor Cold	Jan 6

Month Stem — Five Tiger Trick (五虎遁年起月法):

Year Stem	Month-1 (寅) starts at Stem index
甲 or 己	2 (丙)
乙 or 庚	4 (戊)
丙 or 辛	6 (庚)
丁 or 壬	8 (壬)
戊 or 癸	0 (甲)

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month_offset      = bazi_month_number − 1      (0 for month 1, 1 for month 2 … 11 for month 12)
month_stem_index  = (five_tiger_start + month_offset) % 10

Example: Year stem 庚 (index 6) → five-tiger start = 4 (戊). Birth in March (Bazi month 2, 卯) → month_stem = (4 + 1) % 10 = 5 → 己. Month pillar: 己卯.

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2c. Day Pillar (日柱)

Use the Julian Day Number (JDN) to get a unique integer for each calendar date, then apply the fixed offset.

Step 1 — Compute JDN:

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If M ≤ 2: set Y = Y−1, M = M+12
A = floor(Y / 100)
B = 2 − A + floor(A / 4)
JDN = floor(365.25 × (Y + 4716)) + floor(30.6001 × (M + 1)) + D + B − 1524

Step 2 — Day Stem-Branch:

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delta            = JDN − 2415021        (2415021 = JDN of 1900-01-01)
day_stem_index   = delta % 10           (甲=0, 乙=1, … 癸=9)
day_branch_index = (delta + 10) % 12    (子=0, 丑=1, … 亥=11)

Verification anchor: JDN 2451545 = 2000-01-01 = 戊午日 (delta=36524, stem=4=戊, branch=6=午).

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2d. Hour Pillar (时柱)

1. Map the true-solar-time hour to an Earthly Branch:

   • Hour 23 or 0 → index 0 (子)
   • Otherwise → (hour + 1) // 2

2. Derive the Heavenly Stem using the Five Rat Trick (五鼠遁) from the Day Stem:

Day Stem	子时 starts at Stem index
甲 or 己	0 (甲)
乙 or 庚	2 (丙)
丙 or 辛	4 (戊)
丁 or 壬	6 (庚)
戊 or 癸	8 (壬)

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hour_stem_index = (zi_start_index + branch_index) % 10

Step 3: Ten Gods (十神)

The Ten Gods describe the relationship between any Heavenly Stem and the Day Master (日主 = Day Pillar's Heavenly Stem).

Algorithm — given Day Stem index d and Other Stem index o:

1. Compute Five-Element indices: d_wx = d // 2, o_wx = o // 2
2. Check polarity: same_polarity = (d % 2) == (o % 2)
3. Compute relation: diff = (o_wx - d_wx) % 5

diff	Relationship	Same Polarity	Different Polarity
0	Same as me	比肩 (Companion)	劫财 (Rob Wealth)
1	I produce	食神 (Eating God)	伤官 (Hurting Officer)
2	I control	偏财 (Indirect Wealth)	正财 (Direct Wealth)
3	Controls me	七杀 (Seven Killings)	正官 (Direct Officer)
4	Produces me	偏印 (Indirect Seal)	正印 (Direct Seal)

Step 4: Five Elements Energy Score

For each of the Four Pillars, accumulate scores:

• Each Heavenly Stem contributes 100 points to its element
• Each Hidden Stem in the Earthly Branch contributes its weighted score (see Hidden Stems table above)

Then apply monthly coefficients based on the Month Branch to get seasonal adjustments. The element in season gets a ~2× boost; the element controlled by the season gets ~0.5×.

Step 5: Day Master Strength (日主强弱)

Compute:

• Allies (同党): Elements that are Same-as-me + Produces-me (比劫 + 印)
• Opponents (异党): Elements that I-produce + I-control + Controls-me (食伤 + 财 + 官杀)

If allies score > opponents score → Day Master is Strong (身强) If opponents score > allies score → Day Master is Weak (身弱)

Step 6: Favorable & Unfavorable Elements (用神/忌神)

• Strong Day Master needs to be drained/controlled → Favorable: Food God element, Wealth element, Officer element. Unfavorable: Seal, Companion.
• Weak Day Master needs support → Favorable: Seal element, Companion element. Unfavorable: Food, Wealth, Officer.

Step 7: Major Fortune Cycles (大运)

1. Determine direction: Yang-year + Male OR Yin-year + Female → Forward; otherwise → Reverse
2. Calculate start age: Count days between birth and the next (forward) or previous (reverse) solar term (节); 3 days = 1 year
3. Starting from the Month Pillar, step the Stem-Branch forward or backward for each 10-year cycle

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Lite Interpretation Guide

Day Master Personality Profiles

Day Master	Element	Core Traits
甲	Wood (Yang)	Upright, ambitious, natural leader
乙	Wood (Yin)	Gentle, resilient, adaptable
丙	Fire (Yang)	Passionate, radiant, optimistic
丁	Fire (Yin)	Meticulous, warm, patient
戊	Earth (Yang)	Honest, steady, inclusive
己	Earth (Yin)	Gentle, responsible, nurturing
庚	Metal (Yang)	Resolute, decisive, principled
辛	Metal (Yin)	Refined, precise, persistent
壬	Water (Yang)	Intelligent, dynamic, big-picture thinker
癸	Water (Yin)	Gentle, wise, highly adaptable

Pattern (格局) Quick Guide

The pattern is determined primarily by the Ten God of the Month Pillar's Heavenly Stem:

Pattern	Key Characteristics
食神格 (Eating God)	Creative, expressive, enjoys life
伤官格 (Hurting Officer)	Talented, unconventional, outspoken
正官格 (Direct Officer)	Responsible, disciplined, rule-following
七杀格 (Seven Killings)	Bold, courageous, risk-taking
正印格 (Direct Seal)	Wise, studious, compassionate
偏印格 (Indirect Seal)	Original thinker, perceptive, solitary
正财格 (Direct Wealth)	Pragmatic, good with money, reliable
偏财格 (Indirect Wealth)	Flexible, opportunistic, sociable

Lucky Attributes by Favorable Element

Favorable Element	Lucky Colors	Lucky Direction
木 Wood	Green, Teal	East
火 Fire	Red, Purple	South
土 Earth	Yellow, Brown	Center
金 Metal	White, Gold	West
水 Water	Black, Blue	North

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Output Format

When presenting results to the user, structure the output as:

1. Birth Info — Name, date, time, location, true solar time
2. Four Pillars Chart — Year / Month / Day / Hour pillars with Stem, Branch, Hidden Stems, Ten Gods, and Na-Yin
3. Five Elements Analysis — Score breakdown, strongest/weakest element, missing elements
4. Day Master Analysis — Element, strength (strong/weak/balanced), personality tags
5. Favorable Elements — Yong Shen (用神), Xi Shen (喜神), Ji Shen (忌神), lucky colors, lucky directions
6. Major Fortune Cycles — Start age, 10-year cycle Stem-Branch pairs

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Advanced Features — Available on Compass AI

This skill covers the core calculation and basic interpretation. For a complete, AI-powered fortune experience, visit:

https://fortune.zodi.zone/web/

Advanced features include:

• AI Deep Analysis — Full personality, career, relationship, and health analysis powered by large language models with streaming output
• Life K-Line Chart (人生K线图) — Fortune scores from age 0 to 100, visualized as an interactive chart showing the highs and lows of each life stage
• Two-Person Compatibility (合盘分析) — Compare two birth charts for love, business, or family compatibility with detailed energy dynamics, conflict points, and synergy analysis
• Daily Fortune Stick (每日灵签) — Personalized daily divination based on your Bazi and the current day's energy
• Interactive Fortune Chat (命理对话) — Multi-turn conversation with an AI fortune-teller that remembers your chart and provides deep, contextual guidance
• Fortune Book Management (命书管理) — Save, compare, and revisit birth charts for yourself and your loved ones

Try it now → Compass AI