On Deriving the Lunar Month and Hour Pillars

原文

论遁月日时

夫命以年为本为父，月为兄弟僚友，日为主为妻为己身，时为子孙为帝产为平生荣辱之首。又曰年为根，月为苗，日为花，时为实，故苗无根不生，实无花不结。所以遁月从年，遁时从日。遁月即甲己之年，正月起丙寅，二月丁卯，顺行十二月。
古歌曰：甲已之年丙作首，乙庚之岁戊为头，丙辛之岁寻庚上，丁壬壬位顺行流，更有戊癸何处起？甲寅之上好追求。
遁时如甲子日子时生人即甲己，还加甲，便知子时乃甲子，丑时乃乙丑，顺行十二时。
古歌曰：甲己还加甲，乙庚丙作初，丙辛从戊起，丁壬庚子居，戊癸何方发？壬子是直途。
月时之法，取天干合数，阴阳之配也。既取合数，自生化数，月则取生，时则取克。假如甲己化土，火生土故，月起丙寅；水克土故，时起甲子。月遁起寅，人生于寅之义，东作方兴之时也；时遁起子，天开于子之义，一阳方生之候也。究而言之，则皆相生而转，循环无端焉。盖上古历元年甲子，月甲子，日甲子，时甲子，甲己起，甲子祖于此也。有甲子则乙丑、丙寅顺布十二宫，阳生阳，阴生阴，相间一位，同类为夫妇。是起月之法，不外起时之中矣。

译文

📜 Overall Paraphrase

In Four Pillars of Destiny (BaZi), the Year Pillar symbolizes the foundation and parents 🌳, the Month Pillar represents siblings and friends 👬, the Day Pillar corresponds to oneself and spouse 💑, and the Hour Pillar foretells descendants, wealth, and life's honors and disgraces 🏆. The ancients used plant growth as an analogy: the year is the root, the month is the sprout, the day is the flower, and the hour is the fruit—without a root, the sprout cannot grow; without a flower, the fruit cannot form. Therefore, calculating the Month Pillar must start from the Year Pillar (deriving the month), and calculating the Hour Pillar must start from the Day Pillar (deriving the hour).

Rules for Deriving the Month (Five Tigers Method) 🔥

Determine the starting Heavenly Stem and Earthly Branch of the first lunar month based on the Heavenly Stem of the Year Pillar:

Years with Heavenly Stems Jia (甲) or Ji (己): First month is Bing Yin (丙寅), second month is Ding Mao (丁卯)… sequentially to the twelfth month.
Years with Heavenly Stems Yi (乙) or Geng (庚): First month is Wu Yin (戊寅), second month is Ji Mao (己卯)…
Years with Heavenly Stems Bing (丙) or Xin (辛): First month is Geng Yin (庚寅), second month is Xin Mao (辛卯)…
Years with Heavenly Stems Ding (丁) or Ren (壬): First month is Ren Yin (壬寅), second month is Gui Mao (癸卯)…
Years with Heavenly Stems Wu (戊) or Gui (癸): First month is Jia Yin (甲寅), second month is Yi Mao (乙卯)…

Summary Mnemonic:

In Jia and Ji years, Bing leads the start; in Yi and Geng, Wu Yin is the head.
For Bing and Xin, seek Geng's origin; for Ding and Ren, Ren's position flows.
For Wu and Gui, from where does it spring? Jia Yin is the good pursuit.

Rules for Deriving the Hour (Five Rats Method) 🐭

Determine the starting Heavenly Stem and Earthly Branch of the Zi hour (子时, 11 PM-1 AM) based on the Heavenly Stem of the Day Pillar:

Days with Heavenly Stems Jia (甲) or Ji (己): Zi hour is Jia Zi (甲子), Chou hour is Yi Chou (乙丑)… sequentially through the twelve two-hour periods.
Days with Heavenly Stems Yi (乙) or Geng (庚): Zi hour is Bing Zi (丙子), Chou hour is Ding Chou (丁丑)…
Days with Heavenly Stems Bing (丙) or Xin (辛): Zi hour is Wu Zi (戊子), Chou hour is Ji Chou (己丑)…
Days with Heavenly Stems Ding (丁) or Ren (壬): Zi hour is Geng Zi (庚子), Chou hour is Xin Chou (辛丑)…
Days with Heavenly Stems Wu (戊) or Gui (癸): Zi hour is Ren Zi (壬子), Chou hour is Gui Chou (癸丑)…

Summary Mnemonic:

For Jia and Ji, add Jia again (Jia Zi); for Yi and Geng, Bing begins anew.
For Bing and Xin, start from Wu; for Ding and Ren, Geng Zi resides.
For Wu and Gui, from where does it spring? Ren Zi is the true path.

🧠 In-Depth Understanding

Core Concepts 💡

Yin-Yang Paired with Five Elements: Deriving the month and hour is essentially the deduction based on Heavenly Stem combinations (e.g., Jia-Ji transforms into Earth) and the generation/restraint cycles of the Five Elements (Fire 🔥 generates Earth → month starts with Bing Yin; Water 🌊 restrains Earth → hour starts with Jia Zi).
Unity of Time and Space: The Month Pillar begins at the Yin hour (3-5 AM), as Yin marks the start of the day 🌄, symbolizing the sprouting of all things; the Hour Pillar begins at the Zi hour (midnight), as Zi is the initial birth of Yang energy 🌤, subtly aligning with the cosmic cycle.
Cyclical Law: The arrangement of Stems and Branches follows the pairing rule of "Yang with Yang, Yin with Yin," forming a closed-loop system 🔄.

Modern Interpretation 🌟

Calendar Origins: The Stem-Branch system originated from ancient astronomical observations, transforming the dimension of time into a computable symbolic model 📅.
Demystification: The derivation methods are essentially ancient mathematical formulas, mapping year, month, day, and hour onto the 60 Jiazi cycle through fixed rules, similar to modern coding logic 💻.
Dynamic Interconnection: The Four Pillars do not exist in isolation; the Year and Day Pillars serve as anchors, while the Month and Hour Pillars are derived according to rules, reflecting a holistic view.

Practical Value ⚡

Foundation for Chart Creation: Mastering month and hour derivation is a core skill for constructing a BaZi chart, preventing over-reliance on software and loss of deductive logic.
Decision-Making Reference:
- Selecting Auspicious Times: Combining the energy of the Hour Pillar to choose start times for important matters ⏰ (e.g., signing contracts, travel).
- Trend Analysis: The Month Pillar relates to interpersonal resources, the Hour Pillar to long-term development, aiding career planning 📈.

Philosophical Reflection 🤔

"A sprout cannot grow without a root; a fruit cannot form without a flower" reveals the law of cause and effect in life's growth:

Foundation (Year Pillar) determines developmental potential, while timing (Month & Hour Pillars) influences stage outcomes.

Modern Implication: Personal achievement requires considering both inherent conditions (root) and action nodes (flower); neither can be omitted.

📚 Related Knowledge

Concept	Explanation
Heavenly Stem Combinations	Jia-Ji transforms to Earth, Yi-Geng transforms to Metal, etc. – the basis for changes in Five Elements attributes.
Twelve Growth Stages	The state of waxing/waning of the Five Elements within the lunar month command (e.g., Yin is the "birth" stage for Fire).
Four Pillars Structure	Year Pillar = Macro-environment, Month Pillar = Youth/Young Adulthood, Day Pillar = Middle Age, Hour Pillar = Later Years/Old Age.

Further Reading:

Yuan Hai Zi Ping (Abyssal Sea, Balanced Life) · On Establishing Examples: Details the rules for Stem-Branch deduction.
Wu Xing Jing Ji (The Quintessence of the Five Elements) · Volume Three: Deepens the application of Five Elements generation/restraint in derivation methods.

Modern Research:

Scholar Li Ling, in Examination of Chinese Occult Arts, points out: The Stem-Branch system is an early "time-space-human affairs" correlation model possessing proto-scientific characteristics.
Archaeoastronomy confirms: The 60 Jiazi cycle corresponds to the 12-year orbital period of Jupiter (the Year Star).

💎 Key Reminder: In contemporary application, reinterpretation is needed in light of social changes—
For example, "hour for descendants" can be expanded to "personal legacy and spiritual heritage," and "wealth/property" can be understood as "accumulation of social resources."