Two systems · structural comparison
The comparison is not about which one is right. It is about what each one takes in and hands back: one reads the position of planets against a zodiac anchored at the equinox, the other reads a cycle of stems and branches anchored at the solar terms.
| Dimension | Western astrology | BaZi |
|---|---|---|
| Time granularity | date plus birth moment | date plus birth moment (the hour pillar needs it) |
| Place | required: no place, no houses or ascendant | optional: used only for true-solar-time correction (4 minutes per degree) |
| What anchors the cycle | twelve 30° sectors of the ecliptic, starting at the equinox | solar terms: one node per 30° of solar longitude |
| Reference bodies | actual positions of the planets and Moon | the stem-and-branch cycle, not defined by live planetary positions |
A BaZi year pillar turns at lichun, not at New Year and not at lunar new year. Lichun floats between 3 and 5 February. The engine's table covers 201 years (1900–2100); every entry is computed:
| Lichun falls on | Years | Share |
|---|---|---|
| February 3 | 39 | 19.4% |
| February 4 | 128 | 63.7% |
| February 5 | 34 | 16.9% |
Lichun lands on 3 / 4 / 5 February across the 201-year table — 3 possible dates. The western zodiac year turns at the equinox, in the second half of March (this page does not compute astronomical data; that date is given only for contrast), roughly six weeks later. Between mid-January and mid-March the two calendars therefore disagree about which year you belong to.
Both systems have twelve. That is where the wrong correspondences come from. The twelve branches are bounded by solar terms — one branch is one whole month command. The twelve signs are thirty-degree sectors of the ecliptic starting at the equinox.
| Branch | Node that starts it | Month | Main qi |
|---|---|---|---|
| 子 Zi, Rat | 大雪 Major Snow | 11 | 癸 Gui Water |
| 丑 Chou, Ox | 小寒 Minor Cold | 12 | 己 Ji Earth |
| 寅 Yin, Tiger | 立春 Start of Spring | 1 | 甲 Jia Wood |
| 卯 Mao, Rabbit | 惊蛰 Awakening of Insects | 2 | 乙 Yi Wood |
| 辰 Chen, Dragon | 清明 Clear and Bright | 3 | 戊 Wu Earth |
| 巳 Si, Snake | 立夏 Start of Summer | 4 | 丙 Bing Fire |
| 午 Wu, Horse | 芒种 Grain in Ear | 5 | 丁 Ding Fire |
| 未 Wei, Goat | 小暑 Minor Heat | 6 | 己 Ji Earth |
| 申 Shen, Monkey | 立秋 Start of Autumn | 7 | 庚 Geng Metal |
| 酉 You, Rooster | 白露 White Dew | 8 | 辛 Xin Metal |
| 戌 Xu, Dog | 寒露 Cold Dew | 9 | 戊 Wu Earth |
| 亥 Hai, Pig | 立冬 Start of Winter | 10 | 壬 Ren Water |
There is no "Rat = Aries" mapping. One set of twelve is bounded by nodes, the other by the equinox: they are offset by about six weeks and the offset drifts year to year. Any table that pairs the twelve branches with the twelve signs one-to-one is an invention, and this site does not print it.
| What you can see | Western astrology | BaZi |
|---|---|---|
| Skeleton | planet in sign, house, aspect | four pillars, ten gods, hidden stems |
| Topical split | twelve houses, one per life area | by pillar position and by ten-god group |
| Time technique | transits, progressions, returns | luck pillars (ten-year steps) plus the annual pillar |
| Computed here | no | yes, and every number is checkable |
The usual comparison asks which system is more accurate. This site cannot answer that and will not: it publishes no accuracy rate and no match score against life events. What can be compared is structure — how many inputs, where the cycle turns, which reproducible quantities come out. All three are listed above.
A note on what this page deliberately does not do: the popular versions of this material assign a fixed personality to each term — one character per branch, one destiny per stage. This site rejects that framing. What is published here is a structural position: which element sits where, on what kind of ground, with which tenants inside. The same term reads differently under a different month command, and no meaningful judgement exists without the other characters of the chart. Where the tradition offers a reading it is labelled as the tradition's; this site's own contribution is that every number and term on this page is computed, versioned and checkable against the methodology page.
These are the questions specific to this page; broader conventions live on the methodology page.
Every enumerable component of ba zi has its own page here. Each page is computed by the same engine and can be checked item by item — none of it is a personality table.