✦ FREE BAZI TOOL

Bazi Day Master Calculator

Find your Four Pillars Day Stem — the core of your Chinese astrology chart — in seconds.

🔮 Find Your Day Master

甲

Jia Wood

Jiǎ · Yang Wood · Day Stem
Yang Wood

✦ Core Strengths

    ⚡ Challenges

      What Is a Bazi Day Master?

      In the Four Pillars of Destiny (Bazi), your birth information is encoded into four columns — Year, Month, Day, and Hour. Each column has two components: a Heavenly Stem on top and an Earthly Branch below. The Day Master is specifically the Heavenly Stem of the Day Pillar.

      Unlike the Chinese zodiac (which only uses your birth year), the Day Master is considered the most personal and accurate indicator of your core self in Bazi. It determines how you process life experiences, how you relate to wealth, relationships, career, and how your luck cycles unfold over decades.

      There are 10 Heavenly Stems cycling through five elements (Wood, Fire, Earth, Metal, Water) in two polarities (Yang and Yin). This creates 10 distinct Day Master archetypes, each with a unique personality blueprint.

      The 10 Heavenly Stems — Day Master Reference

      Stem Name Element Polarity Core Archetype
      甲 Jiǎ (Jia) Wood Yang The Oak — natural leader, ambitious, principled, direct
      乙 Yǐ (Yi) Wood Yin The Vine — flexible, diplomatic, resilient, charming
      丙 Bǐng (Bing) Fire Yang The Sun — charismatic, enthusiastic, generous, transparent
      丁 Dīng (Ding) Fire Yin The Candle — intellectual, compassionate, analytical, patient
      戊 Wù (Wu) Earth Yang The Mountain — reliable, steady, loyal, enduring
      己 Jǐ (Ji) Earth Yin The Farmland — nurturing, adaptable, patient, compassionate
      庚 Gēng (Geng) Metal Yang The Sword — courageous, just, decisive, blunt
      辛 Xīn (Xin) Metal Yin The Jewel — elegant, detail-oriented, aesthetic, principled
      壬 Rén (Ren) Water Yang The Ocean — strategic, adaptable, intelligent, restless
      癸 Guǐ (Gui) Water Yin The Rain — intuitive, gentle, empathetic, perceptive

      Day Master vs. Month Pillar: Why Both Matter

      While the Day Master reveals your core identity, the Month Branch (the Earthly Branch of your Month Pillar) determines your Day Master's strength by representing the season of birth. A Yang Wood (Jiǎ) person born in spring is naturally strong — the season supports Wood energy. The same person born in autumn, when Metal dominates, has a Weak Day Master that needs different strategies.

      This is why two people with the same Day Master can have wildly different life paths: their Day Master strength, the supporting pillars, and how their luck cycles interact with their chart determines everything from career timing to relationship patterns.

      Ready for Your Complete Four Pillars Chart?

      The Day Master calculator above gives you the foundation — your core self. But a complete Bazi reading requires all four pillars together: Year, Month, Day, and Hour. That's where the real depth begins.

      The Four Pillars Calculator at fourpillarscalculator.com generates your full Bazi chart in seconds, including:

      Your Day Master is the lens. The full chart is the picture. Most Bazi insights — career timing, relationship compatibility, wealth windows — only emerge when you analyze all four pillars together with the luck cycle overlay.

      Calculate Your Full Bazi Chart →

      How This Calculator Works — Algorithm & Method

      Library: lunar-javascript (astronomy-based) · Deterministic calculation — no AI interpolation

      Core Structures

      StructureCountValues
      Heavenly Stems (天干 Tiāngān)10甲乙丙丁戊己庚辛壬癸 (Jiǎ Yǐ Bǐng Dīng Wù Jǐ Gēng Xīn Rén Guǐ)
      Earthly Branches (地支 Dìzhī)12子丑寅卯辰巳午未申酉戌亥 (Rat→Pig)
      Jiazi Cycle (甲子 cycle)60 days/yearsLCM(10, 12) = 60 — one full stem+branch rotation
      Five Elements (五行 Wǔxíng)5Wood 木 · Fire 火 · Earth 土 · Metal 金 · Water 水
      Polarity (阴阳 Yīnyáng)2Yang (odd stems 1,3,5,7,9) · Yin (even stems 2,4,6,8,10)

      Day Master Calculation Algorithm

      — Step 1: Convert Gregorian date to Chinese solar calendar —
      solar = Solar.fromYmd(year, month, day) ← lunar-javascript library
      lunar = solar.getLunar() ← accounts for solar terms (节气)

      — Step 2: Extract Day Heavenly Stem —
      day_gan = lunar.getDayGan() ← one of: 甲乙丙丁戊己庚辛壬癸

      — Step 3: Map stem → element + polarity —
      stem_index = indexOf(day_gan) in STEMS[0..9]
      element = ELEMENTS[floor(stem_index / 2)] ← pairs: Jiǎ/Yǐ=Wood, Bǐng/Dīng=Fire...
      polarity = (stem_index % 2 == 0) ? "Yang" : "Yin"

      — Step 4: Day Master = Day Stem —
      day_master = day_gan ← the core identity pillar in Bazi

      Stem → Element → Polarity Mapping

      StemPinyinElementPolarity
      甲JiǎWood 木Yang
      乙YǐWood 木Yin
      丙BǐngFire 火Yang
      丁DīngFire 火Yin
      戊WùEarth 土Yang
      己JǐEarth 土Yin
      庚GēngMetal 金Yang
      辛XīnMetal 金Yin
      壬RénWater 水Yang
      癸GuǐWater 水Yin

      Calculation uses the lunar-javascript library for accurate solar term boundary detection. Day Stem may vary by ±1 day for births near midnight or at solar term crossings. For the full 4-pillar chart (Year · Month · Day · Hour) with Ten Gods, strength score, Useful God, and 10-year luck cycles, visit fourpillarscalculator.com.

      Frequently Asked Questions

      The Bazi Day Master (日主, rì zhǔ) is the Heavenly Stem of the Day Pillar in your Four Pillars of Destiny chart. It represents your core self, fundamental nature, and how you interact with the world. There are 10 possible Day Masters, each corresponding to one of the five elements in either Yang or Yin polarity.
      The Day Master is determined by the Heavenly Stem of your birth day according to the Chinese solar calendar. Each day cycles through 10 Heavenly Stems (甲乙丙丁戊己庚辛壬癸) in a repeating 60-day Jiazi cycle. The exact calculation uses the traditional Chinese lunisolar calendar, which accounts for solar terms — not the Gregorian calendar.
      Unlike Western astrology (built around birth year), Bazi centers on the Day Master as the primary identity marker. The Year Pillar describes early life and ancestry. The Month Pillar describes career and parents. But the Day Pillar — specifically its Heavenly Stem — represents YOU: your core personality, how your chart interacts with luck cycles, and your relationship patterns.
      No. The Chinese zodiac sign (rat, ox, tiger, etc.) is based on your birth YEAR and corresponds to the Earthly Branch of the Year Pillar. Your Day Master is the Heavenly Stem of your birth DAY — a completely different and more precise indicator in Bazi. They are separate systems, even though both appear in the Four Pillars chart.
      No — two people born on the same calendar day share the same Day Master (Day Stem). But their full Four Pillars chart differs if they were born at different hours, since the Hour Pillar is unique to each person's birth time and changes the chart's element balance, Ten Gods, and luck pillar timing significantly.
      Day Master strength is determined by whether the elements in your Month Branch (season of birth) and other pillars support or drain your Day Master element. A Strong Day Master needs elements that output, control, or drain it. A Weak Day Master needs its own element or the Resource element. Strength determines your Useful God — the element that brings you luck and balance throughout your life.
      The five elements are Wood, Fire, Earth, Metal, and Water. They interact in two cycles: the Producing Cycle (Water→Wood→Fire→Earth→Metal→Water) and the Controlling Cycle (Wood→Earth→Water→Fire→Metal→Wood). In Bazi, these cycles determine the Ten Gods — the 10 relationship types between your Day Master and every other stem in your chart, which encode career, wealth, relationships, and power dynamics.