Bazi, or "Four Pillars of Destiny," is a classical Chinese astrological system dating back over 1,500 years. It maps your birth moment (year, month, day, hour) to eight Chinese characters — two characters per pillar — revealing your constitutional strengths, weaknesses, and life trajectory. Unlike Western astrology's focus on personality, Bazi addresses destiny, capacity, and life's major cycles.

The Year Pillar derives from your birth year's position in the 60-year cycle. The Month Pillar is determined by the solar term you were born into (not the Western calendar month) — solar terms mark the Sun's position at 15° intervals, shifting 2-3 days each year. The Day Pillar is calculated using astronomical Julian Date formulas. The Hour Pillar requires your local solar time, accounting for timezone and daylight saving. All calculations use classical Chinese stem-branch cycling (Heavenly Stems repeat every 10 years; Earthly Branches every 12 years).

There are two different year boundaries used in Chinese astrology, and they disagree by a few days every year. The popular "lunar zodiac" (the version on restaurant placemats and most pop culture charts) marks each new year at the Lunar New Year, which can fall anywhere from late January to mid-February depending on the moon. Bazi, however, uses Lìchūn (立春), the solar term marking the Beginning of Spring, which falls on or near February 4 every year. This is the boundary professional Bazi practitioners and the classical Ten Thousand Year Calendar (萬年曆) have used for over 1,500 years.

For most birthdays this never matters because Lichun and Lunar New Year usually fall within the same week. But if you were born in the overlap window (roughly late January to mid-February), the two systems can give different animals. Example: in 1983, Lichun was Feb 4 and Lunar New Year was Feb 13. Someone born Feb 5–12, 1983 is Pig in Bazi but Dog on a placemat. We use Lichun because the rest of the Bazi chart (Day Master, Month Pillar, Luck Pillars, Five Elements balance) is anchored to the sun's exact position. If we switched the year to the lunar new year, every other calculation in your chart would no longer line up. Both traditions are real, but only the solar-term boundary keeps the Bazi system internally consistent.

The Day Master is the Heavenly Stem of your Day Pillar — it is your core self, the deepest layer of your personality and constitution. Its strength or weakness relative to the other seven characters reveals your natural resilience, assertiveness, or need for support. A strong Day Master tends toward independence; a weak one toward collaboration. A balanced Day Master embodies flexibility. The Day Master is considered the most important character in a Bazi reading.

Luck Pillars are ten-year periods of your life, each governed by a Heavenly Stem and Earthly Branch. Your first Luck Pillar typically begins at age 3 (or age 1, depending on the school of thought). Each decade activates specific elements and animals, bringing distinct themes, opportunities, and challenges. A favorable Luck Pillar reinforces your chart; an unfavorable one creates obstacles. Skilled Bazi practitioners use Luck Pillars to forecast major life transitions and advise on timing.

This calculator uses classical Bazi algorithms for solar term detection (Meeus Ch25 for the Sun's longitude, Newton-Raphson iteration for exact solar term dates) and accounts for your timezone and daylight saving time. The accuracy of your chart depends on the accuracy of your birth data: time should be within 2 minutes, and location within 50km. Birth certificates in most countries record times to the nearest minute. If your exact time is unknown, a noon default is used, which reduces accuracy. For the most precise reading, consult a professional Bazi master in person.

The Five Elements (五行) — Wood, Fire, Earth, Metal, and Water — form the foundation of Bazi analysis. Each element generates the next (Wood feeds Fire, Fire creates Earth, Earth bears Metal, Metal collects Water, Water nourishes Wood) and controls another (Wood parts Earth, Fire melts Metal, Earth dams Water, Metal chops Wood, Water quenches Fire). Your chart distributes eight characters across these five elements. The balance or imbalance reveals your constitutional strengths, deficiencies, and which elements you need to cultivate or avoid. Feng Shui remedies, career choices, and relationship compatibility are all derived from this elemental analysis.

Western astrology uses the positions of planets in the zodiac to map personality and psychological tendencies. Bazi uses the Chinese calendar's Heavenly Stems and Earthly Branches to map destiny, constitutional capacity, and life cycles. Western astrology asks "who are you?" — Bazi asks "what is your capacity, and when does fate favor you?" The two systems are complementary: Western astrology excels at psychological insight, while Bazi excels at timing and practical guidance. The Cosmos Daily reading engine combines both systems (along with five others) for a unified portrait.

Hidden stems (人元/藏干) are the Heavenly Stems concealed inside each Earthly Branch. Every branch contains one to three hidden stems: a main qi (本气) that is structurally dominant, a middle qi (中气), and sometimes a residual qi (余气). For example, the Tiger branch (寅) hides 甲 Wood (main), 丙 Fire (middle), and 戊 Earth (residual). These hidden stems carry the unconscious drives, latent talents, and the underlying elemental composition that pure character-counting misses. Classical Bazi analysis weights hidden stems alongside visible stems to assess Day Master strength, elemental balance, and Ten Gods relationships. This calculator surfaces all hidden stems with their classical weighting (visible stems and main hidden qi count fully, middle qi at 0.5, residual qi at 0.3).

The Ten Gods (十神) are the ten possible relationships any stem in your chart can have with your Day Master, derived from Five Element generation, control, and the polarity (Yang/Yin) of the stems. They are: 比肩 Friend, 劫财 Rob Wealth, 食神 Eating God, 伤官 Hurting Officer, 偏财 Indirect Wealth, 正财 Direct Wealth, 七杀 Seven Killings, 正官 Direct Officer, 偏印 Indirect Resource, and 正印 Direct Resource. The Ten Gods reveal how each pillar functions in your life — Wealth gods show what you control, Officer gods show what controls you, Resource gods show what supports you, Output gods show what you produce, and Companion gods show your peers. This calculator labels every visible stem and every hidden stem with its Ten God to your Day Master.