# What a chart is made of (/en/docs/guide/concepts)

The minimum Zi Wei Dou Shu you need, readable without code — what a chart is, what parts it has, and what each part decides.



*For: everyone. No code needed to read this; each page ends with a "In code" section*

This chapter does not teach you how to *interpret* a chart. It explains **what a chart is made of**
— read it and you will know what each of those nouns in the output is talking about.

## What charting does [#what-charting-does]

Charting takes four inputs: the **date** of birth, the **hour** of birth, the **gender**, and a set
of **configuration** switches that pin down school and boundary choices.

The output is a chart of fixed shape: **twelve palaces**, each with its own stem and branch, its own
palace name, and however many **stars** land in it. This chart never changes for the rest of a life;
it is called the **natal chart**.

On top of the natal chart, **horoscopes** are projected forward in time: which palaces and which
mutagens govern this decade (the decadal), this year, this month, this day, this hour. Horoscopes
change with the date you query.

```
date of birth + hour + gender + config
        │
        ├─→ natal chart (twelve palaces + stars + mutagens)   ← fixed for life
        │
        └─→ horoscope (decadal/age/yearly/monthly/daily/hourly) ← varies with the target date
```

## Four concepts to get straight first [#four-concepts-to-get-straight-first]

### Stems and branches [#stems-and-branches]

Ten heavenly stems (jia, yi, bing, ding, wu, ji, geng, xin, ren, gui) and twelve earthly branches
(zi, chou, yin, mao, chen, si, woo, wei, shen, you, xu, hai) are paired off in a cycle of sixty and
used to number years, months, days and hours.

The four stem-branch pairs for a moment of birth are the **four pillars** — the
`geng chen - jia shen - bing woo - geng yin` you see in the chart output.

Each of the twelve palaces also carries a heavenly stem of its own (the palace stem), which is what
the flying mutagens are derived from.

### Soul palace and Body palace [#soul-palace-and-body-palace]

The **Soul palace** is the origin of the whole chart, located from the lunar month and hour of
birth. The twelve palace names are laid out starting from it.

The **Body palace** is not a thirteenth palace: it is one of the twelve, additionally marked, and it
indicates where effort is applied in later life.

### Five Elements class [#five-elements-class]

Derived from the stem and branch of the Soul palace. It is one of five values: water 2nd, wood 3rd,
metal 4th, earth 5th, fire 6th. The number (2 to 6) is used twice further on:

1. **Placing Ziwei**: the lunar day is divided by the class number to fix which palace Ziwei falls
   in — and the positions of all fourteen major stars unfold from that one step.
2. **Fixing the starting age of the decadals**: water 2nd starts at nominal age 2, fire 6th at 6,
   and each palace governs ten years from there.

<Callout title="Nominal age">
  **Nominal age** (虚岁) is East Asian age reckoning: you are 1 at birth and gain a year at the turn of
  the year, not on your birthday. Every age quoted in a chart — decadal ranges, age-fortune years — is
  a nominal age, so it runs one or two ahead of the age on your passport.
</Callout>

### Mutagens [#mutagens]

Each heavenly stem carries an assignment of four mutagens — Wealth (禄), Power (权), Status (科),
Trouble (忌) — pointing at four specific stars. When charting, the birth year's stem stamps its
mutagens onto the corresponding stars; each horoscope level then has mutagens of its own.

This is the main source of dynamic information in Zi Wei Dou Shu. See
[Mutagens and flying stars](/en/docs/guide/concepts/mutagen).

## How the chart is laid out [#how-the-chart-is-laid-out]

A Zi Wei chart is twelve cells arranged in a ring, each cell owned by one **earthly branch**. The
twelve palaces in the output are stored in a fixed order, and **slot 0 is the Yin palace**:

| Slot   | 0   | 1   | 2    | 3  | 4   | 5   | 6    | 7   | 8  | 9   | 10 | 11   |
| ------ | --- | --- | ---- | -- | --- | --- | ---- | --- | -- | --- | -- | ---- |
| Branch | yin | mao | chen | si | woo | wei | shen | you | xu | hai | zi | chou |

<Callout type="warn">
  The slot order follows the **branches**, not the palace names. The Soul palace can land in any one
  of the twelve cells, and slot 0 is not necessarily the Soul palace. Look palaces up by name; never
  hard-code a slot index.
</Callout>

The twelve **palace names** (Soul, Parents, Spirit, …) are what charting computes: starting from the
cell holding the Soul palace, they are laid out counter-clockwise. So "which cell holds the Soul
palace" differs from chart to chart — which is exactly what the first step of charting decides. See
[The twelve palaces](/en/docs/guide/concepts/palaces).

## The layers of information on a chart [#the-layers-of-information-on-a-chart]

<Files>
  <Folder name="Astrolabe">
    <File name="solar_date / lunar_date / chinese_date — the birthday in three calendars" />

    <File name="time / time_range — the hour and the clock range it covers" />

    <File name="sign / zodiac — zodiac sign and zodiac animal" />

    <File name="soul / body — soul star and body star" />

    <File name="five_elements_class — Five Elements class; decides Ziwei placement and the decadal starting age" />

    <Folder name="palaces[12]">
      <File name="name — palace name (soul, wealth, spouse, …)" />

      <File name="heavenly_stem / earthly_branch — the palace stem and branch" />

      <File name="is_body_palace / is_original_palace — Body palace / Original palace flags" />

      <File name="major_stars / minor_stars / adjective_stars — the three star groups" />

      <File name="changsheng12 / boshi12 / jiangqian12 / suiqian12 — the four groups of twelve gods" />

      <File name="decadal — the decadal range this palace governs, plus its stem and branch" />

      <File name="ages — the age-fortune nominal ages that pass through this palace" />
    </Folder>
  </Folder>
</Files>

For the type and meaning of every field, see the [Data model](/en/docs/guide/data-model).

## Read on [#read-on]

<Cards>
  <Card title="Stems, branches and elements" href="/en/docs/guide/concepts/stems-branches" description="What each pillar drives, how yin and yang set direction, where palace stems come from" />

  <Card title="The twelve palaces" href="/en/docs/guide/concepts/palaces" description="Palace names, palace stems, Body palace, Original palace, decadals and age fortune" />

  <Card title="Stars" href="/en/docs/guide/concepts/stars" description="The three star groups, brightness, the four groups of twelve gods, and a star-name table" />

  <Card title="Mutagens and flying stars" href="/en/docs/guide/concepts/mutagen" description="Wealth, Power, Status, Trouble; self-mutagens; flying predicates" />

  <Card title="Surrounded palaces" href="/en/docs/guide/concepts/surrounded" description="A palace is read together with its opposite and its two trine palaces" />

  <Card title="Horoscopes" href="/en/docs/guide/concepts/horoscope" description="What each of the six time scopes computes" />

  <Card title="How charting works" href="/en/docs/guide/concepts/how-it-works" description="Nine steps from birth data to a complete natal chart" />
</Cards>