- Four Pillars (BaZi) 四柱 · 八字 · sì zhù · bā zì
- The year, month, day, and hour of birth, each written as a pair of one Heavenly Stem and one Earthly Branch. The four pairs make eight characters, which is what “BaZi” means.
- Heavenly Stems 天干 · tiān gān
- Ten characters that cycle in a fixed order. Each carries one of the Five Elements and a yang or yin polarity. The top character of every pillar is a stem.
- Earthly Branches 地支 · dì zhī
- Twelve characters, familiar in the West as the twelve zodiac animals. They mark years, months, days, and two-hour periods. The bottom character of every pillar is a branch.
- Day Master 日主 · 日元 · rì zhǔ · rì yuán
- The stem of the day pillar. It represents the person in the chart, and every other character is read by its relationship to it.
- Five Elements 五行 · wǔ xíng
- Wood, Fire, Earth, Metal, and Water. In the generating cycle wood feeds fire, fire makes earth, earth yields metal, metal carries water, and water nourishes wood. In the controlling cycle wood restrains earth, earth dams water, water quenches fire, fire melts metal, and metal cuts wood.
- Hidden stems 藏干 · cáng gān
- Each Earthly Branch contains one to three stems: a main stem and sometimes middle and residual stems. They let a branch contribute more than one element to the chart.
- Ten Gods 十神 · shí shén
- Ten labels for how each stem relates to the Day Master: same element, producing it, produced by it, controlling it, or controlled by it, each split by matching or opposite polarity. They group into five families: companion, resource, output, wealth, and authority.
- Solar terms 节气 · jié qì
- Twenty-four points on the sun’s yearly path, 15° apart. Twelve of them, the jie (节), start the BaZi months. The year changes at Lichun (立春), around February 4, not at Lunar New Year.
- True (apparent) solar time 真太阳时 · zhēn tài yáng shí
- Clock time corrected for your birthplace’s longitude within its time zone and for the equation of time, the sun’s seasonal drift. The hour pillar is based on it, so the same clock time can fall in different two-hour periods in different cities.
- Luck cycles (Major luck) 大运 · dà yùn
- A sequence of 10-year pillars that follows the month pillar forward or backward. Each cycle describes the backdrop, or “climate,” of a decade of life.
- Annual pillar 流年 · liú nián
- The stem-branch pair of a calendar year, read against the natal chart and the current luck cycle to describe that year’s emphasis.
- Useful god (favorable element) 用神 · yòng shén
- The element that best balances a chart. Classical schools choose it in different ways, so instead of naming a single element LuckTime rates each element as supportive, conditional, or cautionary and describes a balancing direction.
- Combinations, clashes, harms, and punishments 合 · 冲 · 害 · 刑 · hé · chōng · hài · xíng
- Fixed relationships between stems or branches. A clash is an opposing pair, a combination is a pair or group that bonds, and harms and punishments are strained pairings. LuckTime reports them as coordination or tension, not as lucky or unlucky signs.
A branch’s element is that of its main hidden stem. The two-hour period is in local true solar time.