{ "heading": "Bazi Calculation Algorithm: How the Four Pillars Are Computed", "body": "Understanding the Bazi calculation algorithm is essential for anyone who wants to compute Four Pillars charts manually or understand how digital calculators work. This comprehensive guide explains the mathematical and astronomical principles behind Bazi computation.\\n\\n## Overview of Bazi Calculation\\n\\n### What Is Bazi Calculation?\\n\\nBazi calculation involves:\\n\\n- Converting solar date to lunar calendar\\n- Determining Heavenly Stems\\n- Determining Earthly Branches\\n- Computing four pillars\\n- Calculating luck pillars\\n\\n### Required Input Data\\n\\nTo calculate Bazi, you need:\\n\\n- Birth year (4 digits)\\n- Birth month (1-12)\\n- Birth day (1-31)\\n- Birth hour (0-23)\\n- Birth minute (0-59)\\n- Birth location (city, country)\\n- Gender (for luck pillar direction)\\n\\n### Output Components\\n\\nBazi calculation produces:\\n\\n- Year pillar (2 characters)\\n- Month pillar (2 characters)\\n- Day pillar (2 characters)\\n- Hour pillar (2 characters)\\n- Luck pillar timeline\\n- Annual fortune charts\\n\\n## Year Pillar Calculation\\n\\n### The Li Chun Boundary\\n\\n**Critical Rule:**\\n\\n- Year changes at Li Chun (立春)\\n- Not at January 1st\\n- Not at Chinese New Year\\n- Usually February 3-5\\n- Solar term based\\n\\n**Li Chun Dates:**\\n\\n- 2024: February 4, 2024\\n- 2025: February 3, 2025\\n- 2026: February 4, 2026\\n- Varies slightly each year\\n- Based on sun position\\n\\n### Calculation Method\\n\\n**Step 1: Determine Year**\\n\\n- If born before Li Chun: Previous year\\n- If born after Li Chun: Current year\\n- Example: Feb 1, 2024 = Gui Mao (2023)\\n- Example: Feb 5, 2024 = Jia Chen (2024)\\n\\n**Step 2: Calculate Heavenly Stem**\\n\\nFormula: (Year - 4) mod 10\\n\\n- 0 = Jia (甲)\\n- 1 = Yi (乙)\\n- 2 = Bing (丙)\\n- 3 = Ding (丁)\\n- 4 = Wu (戊)\\n- 5 = Ji (己)\\n- 6 = Geng (庚)\\n- 7 = Xin (辛)\\n- 8 = Ren (壬)\\n- 9 = Gui (癸)\\n\\n**Step 3: Calculate Earthly Branch**\\n\\nFormula: (Year - 4) mod 12\\n\\n- 0 = Zi (Rat) 子\\n- 1 = Chou (Ox) 丑\\n- 2 = Yin (Tiger) 寅\\n- 3 = Mao (Rabbit) 卯\\n- 4 = Chen (Dragon) 辰\\n- 5 = Si (Snake) 巳\\n- 6 = Wu (Horse) 午\\n- 7 = Wei (Goat) 未\\n- 8 = Shen (Monkey) 申\\n- 9 = You (Rooster) 酉\\n- 10 = Xu (Dog) 戌\\n- 11 = Hai (Pig) 亥\\n\\n### Example Calculation\\n\\n**For 2024:**\\n\\n- Stem: (2024 - 4) mod 10 = 0 = Jia\\n- Branch: (2024 - 4) mod 12 = 4 = Chen\\n- Year Pillar: Jia Chen (甲辰)\\n\\n**For 2025:**\\n\\n- Stem: (2025 - 4) mod 10 = 1 = Yi\\n- Branch: (2025 - 4) mod 12 = 5 = Si\\n- Year Pillar: Yi Si (乙巳)\\n\\n## Month Pillar Calculation\\n\\n### Solar Term Boundaries\\n\\n**Month Changes at Solar Terms:**\\n\\n- Not on 1st of lunar month\\n- Based on sun longitude\\n- Approximately every 15 days\\n- 12 major solar terms\\n- Precise astronomical calculation\\n\\n**12 Major Solar Terms:**\\n\\n1. Li Chun (立春): Feb 3-5 - Tiger month starts\\n2. Jing Zhe (惊蛰): Mar 5-7 - Rabbit month starts\\n3. Qing Ming (清明): Apr 4-6 - Dragon month starts\\n4. Li Xia (立夏): May 5-7 - Snake month starts\\n5. Mang Zhong (芒种): Jun 5-7 - Horse month starts\\n6. Xiao Shu (小暑): Jul 6-8 - Goat month starts\\n7. Li Qiu (立秋): Aug 7-9 - Monkey month starts\\n8. Bai Lu (白露): Sep 7-9 - Rooster month starts\\n9. Han Lu (寒露): Oct 8-9 - Dog month starts\\n10. Li Dong (立冬): Nov 7-8 - Pig month starts\\n11. Da Xue (大雪): Dec 6-8 - Rat month starts\\n12. Xiao Han (小寒): Jan 5-7 - Ox month starts\\n\\n### Month Branch Fixed Assignment\\n\\n**Month to Branch Mapping:**\\n\\n- Tiger (寅): Feb 3-5 to Mar 4-6 (1st lunar month)\\n- Rabbit (卯): Mar 5-7 to Apr 3-5 (2nd lunar month)\\n- Dragon (辰): Apr 4-6 to May 4-6 (3rd lunar month)\\n- Snake (巳): May 5-7 to Jun 4-6 (4th lunar month)\\n- Horse (午): Jun 5-7 to Jul 5-7 (5th lunar month)\\n- Goat (未): Jul 6-8 to Aug 6-8 (6th lunar month)\\n- Monkey (申): Aug 7-9 to Sep 6-8 (7th lunar month)\\n- Rooster (酉): Sep 7-9 to Oct 7-9 (8th lunar month)\\n- Dog (戌): Oct 8-9 to Nov 6-8 (9th lunar month)\\n- Pig (亥): Nov 7-8 to Dec 6-8 (10th lunar month)\\n- Rat (子): Dec 6-8 to Jan 4-6 (11th lunar month)\\n- Ox (丑): Jan 5-7 to Feb 3-5 (12th lunar month)\\n\\n### Month Stem Calculation - Five Tiger Escape\\n\\n**Five Tiger Escape Method (五鼠遁):**\\n\\nBased on year stem, determine first month stem:\\n\\n**Jia or Ji Year (甲/己年):**\\n\\n- Tiger month = Bing Yin (丙寅)\\n- Sequence: Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui, Jia, Yi, Bing, Ding\\n\\n**Yi or Geng Year (乙/庚年):**\\n\\n- Tiger month = Wu Yin (戊寅)\\n- Sequence: Wu, Ji, Geng, Xin, Ren, Gui, Jia, Yi, Bing, Ding, Wu, Ji\\n\\n**Bing or Xin Year (丙/辛年):**\\n\\n- Tiger month = Geng Yin (庚寅)\\n- Sequence: Geng, Xin, Ren, Gui, Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin\\n\\n**Ding or Ren Year (丁/壬年):**\\n\\n- Tiger month = Ren Yin (壬寅)\\n- Sequence: Ren, Gui, Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui\\n\\n**Wu or Gui Year (戊/癸年):**\\n\\n- Tiger month = Jia Yin (甲寅)\\n- Sequence: Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui, Jia, Yi\\n\\n### Example Calculation\\n\\n**For Jia Chen Year (2024), 5th Month:**\\n\\n- Jia year: Tiger month = Bing Yin\\n- Count to 5th month: Bing, Ding, Wu, Ji, Geng\\n- 5th month (Horse) = Geng Wu (庚午)\\n- Month Pillar: Geng Wu\\n\\n## Day Pillar Calculation\\n\\n### Complexity of Day Calculation\\n\\n**Why Day Is Complex:**\\n\\n- No simple formula\\n- Requires astronomical data\\n- Continuous 60-day cycle\\n- Never interrupted\\n- Must reference tables\\n\\n### Calculation Methods\\n\\n**Method 1: Reference Date**\\n\\n- Use known reference day\\n- Count days difference\\n- Apply 60-day cycle\\n- Account for leap years\\n- Calculate remainder\\n\\n**Method 2: Astronomical Algorithm**\\n\\n- Use solar position\\n- Calculate Julian day\\n- Apply formula\\n- Convert to sexagenary\\n- Verify with tables\\n\\n**Method 3: Lookup Tables**\\n\\n- Use perpetual calendar\\n- Find year and month\\n- Locate specific day\\n- Read stem-branch\\n- Most accurate\\n\\n### Reference Date Method\\n\\n**Known Reference:**\\n\\n- January 1, 1900 = Jia Wu (甲午)\\n- Calculate days since\\n- Apply mod 60\\n- Find stem-branch\\n\\n**Formula:**\\n\\n1. Calculate total days from reference\\n2. Add leap year days\\n3. Total days mod 60\\n4. Map to stem-branch\\n5. Verify accuracy\\n\\n### Stem Calculation\\n\\n**Day Stem Formula:**\\n\\n- Stem = (Day number in cycle) mod 10\\n- 0 = Jia, 1 = Yi, 2 = Bing...\\n- Continuous cycle\\n- Never resets\\n- Astronomical basis\\n\\n### Branch Calculation\\n\\n**Day Branch Formula:**\\n\\n- Branch = (Day number in cycle) mod 12\\n- 0 = Zi, 1 = Chou, 2 = Yin...\\n- Continuous cycle\\n- Never resets\\n- Astronomical basis\\n\\n## Hour Pillar Calculation\\n\\n### Two-Hour Periods\\n\\n**12 Two-Hour Blocks:**\\n\\n- Zi (Rat): 23:00-01:00\\n- Chou (Ox): 01:00-03:00\\n- Yin (Tiger): 03:00-05:00\\n- Mao (Rabbit): 05:00-07:00\\n- Chen (Dragon): 07:00-09:00\\n- Si (Snake): 09:00-11:00\\n- Wu (Horse): 11:00-13:00\\n- Wei (Goat): 13:00-15:00\\n- Shen (Monkey): 15:00-17:00\\n- You (Rooster): 17:00-19:00\\n- Xu (Dog): 19:00-21:00\\n- Hai (Pig): 21:00-23:00\\n\\n### Hour Branch Assignment\\n\\n**Fixed by Time:**\\n\\n- Branch determined by birth hour\\n- No calculation needed\\n- Universal system\\n- Consistent always\\n- Simple lookup\\n\\n### Hour Stem - Five Rat Escape\\n\\n**Five Rat Escape Method (五鼠遁):**\\n\\nBased on day stem, determine Zi hour stem:\\n\\n**Jia or Ji Day (甲/己日):**\\n\\n- Zi hour = Jia Zi (甲子)\\n- Sequence: Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui, Jia, Yi\\n\\n**Yi or Geng Day (乙/庚日):**\\n\\n- Zi hour = Bing Zi (丙子)\\n- Sequence: Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui, Jia, Yi, Bing, Ding\\n\\n**Bing or Xin Day (丙/辛日):**\\n\\n- Zi hour = Wu Zi (戊子)\\n- Sequence: Wu, Ji, Geng, Xin, Ren, Gui, Jia, Yi, Bing, Ding, Wu, Ji\\n\\n**Ding or Ren Day (丁/壬日):**\\n\\n- Zi hour = Geng Zi (庚子)\\n- Sequence: Geng, Xin, Ren, Gui, Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin\\n\\n**Wu or Gui Day (戊/癸日):**\\n\\n- Zi hour = Ren Zi (壬子)\\n- Sequence: Ren, Gui, Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui\\n\\n### Example Calculation\\n\\n**For Jia Day, 10:30 AM:**\\n\\n- Jia day: Zi hour = Jia Zi\\n- 10:30 AM = Si hour (Snake)\\n- Count: Jia (Zi), Yi (Chou), Bing (Yin), Ding (Mao), Wu (Chen), Ji (Si)\\n- Hour Pillar: Ji Si (己巳)\\n\\n## Time Zone and Solar Time\\n\\n### Local Solar Time\\n\\n**Why Adjustment Needed:**\\n\\n- Standard time zones are political\\n- Solar time based on sun position\\n- Longitude affects solar time\\n- 4 minutes per degree\\n- Critical for hour pillar\\n\\n### Calculation Formula\\n\\n**Solar Time Adjustment:**\\n\\n1. Find birth longitude\\n2. Find time zone central meridian\\n3. Calculate difference\\n4. Multiply by 4 minutes\\n5. Add/subtract from clock time\\n\\n**Example:**\\n\\n- Birth: Shanghai (121.5°E)\\n- Time zone: UTC+8 (120°E central)\\n- Difference: 1.5 degrees\\n- Adjustment: 1.5 × 4 = 6 minutes\\n- Solar time: Clock time + 6 minutes\\n\\n### Daylight Saving Time\\n\\n**DST Adjustment:**\\n\\n- Check if DST was in effect\\n- Subtract 1 hour if yes\\n- Then apply solar adjustment\\n- Historical DST varies\\n- Research local history\\n\\n## Luck Pillar Calculation\\n\\n### Starting Age\\n\\n**Calculation Method:**\\n\\n- Count days to next solar term (male Yang, female Yin)\\n- Count days to previous solar term (male Yin, female Yang)\\n- Divide by 3\\n- Result = starting age\\n- Remainder = months\\n\\n### Direction Determination\\n\\n**Yang Year Male / Yin Year Female:**\\n\\n- Forward direction\\n- Next solar terms\\n- Progressive sequence\\n\\n**Yin Year Male / Yang Year Female:**\\n\\n- Reverse direction\\n- Previous solar terms\\n- Regressive sequence\\n\\n### Luck Pillar Sequence\\n\\n**Based on Month Pillar:**\\n\\n- Forward: Next stem-branch in sequence\\n- Reverse: Previous stem-branch in sequence\\n- Each pillar = 10 years\\n- Continuous cycle\\n- Lifetime coverage\\n\\n## Conclusion\\n\\nBazi calculation is a sophisticated system combining astronomical observation, mathematical formulas, and traditional methods. Understanding the algorithm helps you appreciate the precision of Four Pillars astrology and verify calculator accuracy.\\n\\nWhile modern calculators automate these calculations, knowing the underlying principles allows you to understand the logic, verify results, and gain deeper insight into the structure of your destiny chart.\n\n## Frequently Asked Questions\n\n### What is the most important pillar in a Bazi chart?\n\nThe Day Pillar is considered the most important as the Day Master (日主) — the Heavenly Stem of the Day Pillar — represents the self. All other elements in the chart are interpreted in relation to the Day Master to determine personality, relationships, career, and destiny patterns.\n\n### How accurate is Bazi destiny analysis?\n\nBazi accuracy depends heavily on having the correct birth time. Even a one-hour difference can change the Hour Pillar and affect the entire chart reading. With accurate birth data, experienced Bazi practitioners can identify personality traits, career tendencies, and major life event timing with notable precision.\n\n### How does Bazi differ from Western astrology?\n\nBazi uses the Chinese Solar Calendar and focuses on Four Pillars derived from birth year, month, day, and hour — each represented by two characters. Western astrology uses planetary positions at birth. Bazi emphasizes Five Element balance and Luck Pillar timing, while Western astrology focuses on planetary archetypes and transits.\n\n### What are the Ten Gods in Bazi analysis?\n\nThe Ten Gods (十神) are ten archetypal relationship patterns between the Day Master and each other element in the chart: Direct Wealth, Indirect Wealth, Direct Officer, Seven Killings, Direct Resource, Indirect Resource, Eating God, Hurting Officer, Friend, and Rob Wealth. They reveal how different life areas (career, money, relationships) manifest.\n\n## Explore More Bazi Tools\n\n- [Free Bazi Calculator](/bazi/calculator) — Generate your Four Pillars chart\n- [Bazi Compatibility](/bazi/compatibility) — Relationship analysis\n- [Bazi Chart Reading](/bazi/reading) — Professional interpretation guide\n- [Learn Bazi](/learning/bazi) — Complete study curriculum", "faqs": [ { "question": "What is the most important pillar in a Bazi chart?", "answer": "The Day Pillar is considered the most important as the Day Master (日主) — the Heavenly Stem of the Day Pillar — represents the self. All other elements in the chart are interpreted in relation to the Day Master to determine personality, relationships, career, and destiny patterns." }, { "question": "How accurate is Bazi destiny analysis?", "answer": "Bazi accuracy depends heavily on having the correct birth time. Even a one-hour difference can change the Hour Pillar and affect the entire chart reading. With accurate birth data, experienced Bazi practitioners can identify personality traits, career tendencies, and major life event timing with notable precision." }, { "question": "How does Bazi differ from Western astrology?", "answer": "Bazi uses the Chinese Solar Calendar and focuses on Four Pillars derived from birth year, month, day, and hour — each represented by two characters. Western astrology uses planetary positions at birth. Bazi emphasizes Five Element balance and Luck Pillar timing, while Western astrology focuses on planetary archetypes and transits." }, { "question": "What are the Ten Gods in Bazi analysis?", "answer": "The Ten Gods (十神) are ten archetypal relationship patterns between the Day Master and each other element in the chart: Direct Wealth, Indirect Wealth, Direct Officer, Seven Killings, Direct Resource, Indirect Resource, Eating God, Hurting Officer, Friend, and Rob Wealth. They reveal how different life areas (career, money, relationships) manifest." } ] }