Sun signs and Zi Wei Dou Shu: why the same sign can have any Life Palace star

A common first question about Zi Wei Dou Shu (Purple Star Astrology) goes like this: "I'm a Scorpio, so which star am I?" The honest answer is that there is no match between the two. One Scorpio can have Zi Wei in the Life Palace, another Tan Lang, and a third no main star at all. This page uses one set of numbers and one real date to show why.

The short version:

• Your sun sign depends only on which stretch of the year your birthday falls in. Zi Wei Dou Shu uses your lunar year, month and day, plus your birth double-hour.
• We cast one chart for every day and every double-hour from 1950 to 2009, 262,980 charts in all. In every sign, each of the fourteen main stars sits in the Life Palace 8.2–8.4% of the time, and the Life Palace is empty 16.4–16.7% of the time.
• A sign roughly covers two neighbouring lunar months. The month and the double-hour place the Life Palace; which star sits there depends on the lunar day and the Five Elements Bureau.
• The only way to find your Life Palace star is to cast your chart, or use the Life Palace star lookup.

What each system looks at

A sun sign is about where the sun stood along the ecliptic on the day you were born. The ecliptic is split into twelve parts of about a month each, so your birthday sets your sign, and the hour plays no part. "Scorpios run deep" and "Aries charge ahead" are descriptions at this level, shared by everyone born in the same stretch of weeks.

Zi Wei Dou Shu works at another level. It converts your birth year, month, day and hour to the lunar calendar and lays out a birth chart of twelve palaces: Life, Siblings, Spouse, Wealth and so on, each holding different stars. When people say "I'm a Tian Ji person", they mean the main star in their Life Palace. This level needs the hour. Move one double-hour and the Life Palace moves one palace.

Both systems start from your birthday, but they cut it very differently. Astrology divides the year into twelve. Zi Wei divides a single day into twelve double-hours, and each of those gives different stars depending on the lunar day and the year. Zi Wei also has a star called Tai Yang, the Sun, which is one of the fourteen main stars and has nothing to do with your sun sign.

The numbers: all twelve signs look the same

We ran Xingge's chart engine from January 1, 1950 to December 31, 2009: twelve charts a day, one per double-hour, 262,980 charts in total. We then grouped them by sun sign and counted the Life Palace stars. This counts each date and hour once, which is not the same as real birth numbers, but it answers one question well: does any sign get a particular star more often?

It doesn't.

• Counting each of the fourteen main stars on its own (when two share the palace, both count), every star sits in the Life Palace 8.2–8.4% of the time in all twelve signs. Fourteen stars rotating through twelve palaces gives one in twelve, about 8.3%, in theory too.
• An Empty Palace, a Life Palace with no main star, comes up 16.4–16.7% of the time in every sign. An average chart has about two palaces without a main star, so the Life Palace lands on one of them about one time in six.

The table above uses this count: one row per sign, with the lowest and highest share among the fourteen main stars in the last column. The twelve rows are almost identical.

The bottom line is short: your sun sign can't tell you which star is in your Life Palace.

Why your sign can't predict your Life Palace

Step one: the sign maps to lunar months. Each sign starts close to one of the "middle" solar terms. Aries starts at the Spring Equinox, Taurus at Grain Rain, Gemini at Grain Buds, and so on to Pisces at Rain Water. Each lunar month contains one of these terms, so the birthdays in one sign mostly fall in two neighbouring lunar months. Scorpio starts at Frost Descent, so Scorpio birthdays fall in the ninth or tenth lunar month.

Step two: the month and the hour place the Life Palace. The method in the Zi Wei Dou Shu Quan Shu (The Complete Book of Zi Wei Dou Shu) counts forward from the Yin palace as the first month to your birth month, then treats that palace as the Zi hour and counts backward to your birth hour. Where the count stops is your Life Palace. So the same month with a different hour gives a different branch. That is why each sign page has an hour table in which every double-hour points to two branches, about half each. For a Scorpio born in the Zi hour, the Life Palace is in Hai about 50.3% of the time and in Xu about 49.7%.

Step three: which main star sits in the Life Palace depends on where the Zi Wei star lands. Its position comes from your lunar birth day and your Five Elements Bureau, and the Bureau comes from the heavenly stem of your birth year and the branch of your Life Palace. A sign spans about thirty days. Over decades, every lunar day from the first to the thirtieth comes around, and all ten year stems cycle through several times. Mix the days and years together and the Zi Wei star can land in any palace, so all fourteen main stars spread evenly across every sign.

At most, your sign narrows your Life Palace down to two palaces, and only if you already know your hour. Which star sits there, the sign can't say.

One day, twelve double-hours

A real date makes this clear. Here are twelve charts for November 3, 1993 (a Scorpio birthday, the twentieth day of the ninth lunar month), one per double-hour:

One day, one sign, and the twelve charts already show seven different Life Palace stars (Tian Ji, Tian Fu, Tai Yang, Zi Wei, Lian Zhen, Tian Tong, Tan Lang) plus two Empty Palaces. Three of them side by side:

• Si hour: Zi Wei with Qi Sha. Zi Wei is the emperor star and Qi Sha the general. People with this pair have firm views, like to set their own direction, and tend to carry a task all the way once it is theirs.
• Shen hour: Empty Palace, borrowing Tai Yang and Ju Men from the opposite palace. With no main star of its own, the Life Palace is read through the palace across from it. These people tend to adjust to their surroundings and show a different side in different settings.
• Xu hour: Tan Lang. Tan Lang people are curious, with many interests. They like meeting people and trying new things, and social settings rarely make them shy.

A few hours apart, the Life Palace goes from someone who wants to lead, to someone who reads the room, to someone who wants to explore. One more detail in the table: the Si and Hai hours both give Zi Wei with Qi Sha, and the Zi and Wu hours both give Tian Ji with Tian Liang. Each pair sits in opposite palaces, so the main stars are laid out the same way, just turned halfway round the chart. What differs is the Bureau and the stars placed by the hour, such as Wen Chang and Wen Qu, so up close they are still two different charts.

Your sign sets the date layer. The hour and the lunar day set your Life Palace.

Reading the twelve sign pages

Click a sign in the table above to open its page. Each one has an hour table showing which two palaces the Life Palace usually falls in for that sign, plus an example of one day across different hours. To see your own, use the form above to cast your chart.