Ba Zi, the “eight characters”, is the Chinese birth chart: four pillars for the year, month, day and hour of birth, each made of a heavenly stem and an earthly branch. This tool works out all four from your birth date, time and place, names your Day Master, the stem of the day that stands for you, and counts the five elements in the chart, showing every step.
How it works
Each pillar is one of the 60 pairs of the sexagenary cycle, made by running the ten stems (Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui) beside the twelve branches (Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, Hai).
- Year. The Ba Zi year starts at Li Chun, the start of spring, when the Sun reaches 315 degrees of longitude, around 4 February. It does not start at the lunar new year.
- Month. The months are solar, not lunar: each starts at one of the twelve solar terms that begin a month, when the Sun reaches 315, 345, 15 degrees and so on, every 30 degrees. The first month is the Tiger month, from Li Chun. Its stem follows from the year stem by the standard rule.
- Day. The day of the sixty-day cycle of days, which runs on regardless of months and years.
- Hour. One of twelve two-hour periods, the first, Zi, running from 11 PM to 1 AM. Its stem follows from the day stem by the standard rule.
The Sun’s positions come from NASA JPL DE440, the same data as our other astronomy tools, so the start of each month is found to the minute. Your birth time is turned into world time with the time zone of your birth place on that date, daylight saving included.
Reading the result
The four pillars are shown as charts usually write them, from the hour on the left to the year on the right, each with its stem above and its branch below, their elements and yin or yang, and the animal of the branch. In the Ziping method, named after Xu Ziping of the Song dynasty, the stem of the day pillar, the Day Master, stands for the person, and the rest of the chart is read around it.
The table of the five elements is a plain count of the eight characters by their own element. Practitioners go further: they count the stems hidden inside the branches, weigh the month most, and look at how the elements support or restrain each other. Treat the count as a first look, not a reading.
If your birth is within two hours of the solar term that changes the month, the result says so, because a small error in the recorded time could change the month pillar.
Where traditions differ
- The clock for the hour. Some use standard time at the birth place, with any daylight saving taken off; others use local mean solar time, from the longitude, or true solar time, which also allows for the uneven speed of the Sun. The tool offers the first two and tells you when the other one would give a different hour or day pillar. For standard time it takes the standard offset of the birth place’s time zone from the IANA time zone database, the record of the world’s clocks that computers use. So war time, which India kept from 1941 to 1945 and the United States from 1942 to 1945, and Britain’s double summer time count as daylight saving and are taken off, even in years when the clocks kept them all year.
- The day change. Some change the day pillar at 11 PM, when the Zi hour begins; others at midnight. Both rules give the hour from 11 PM the next day’s stem. You can choose.
- The southern hemisphere. Whether the months should be reversed for births south of the equator, where the seasons are reversed, is debated. This tool does not reverse them.
How we checked it
We compared the pillars with an independent Chinese calendar program, which has its own model of the Sun, for 9,230 births: the 8 test charts we use for all our tools, ten minutes either side of every month-changing solar term from 1901 to 2074 (2,088 terms), 400 births after 11 PM under both day-change rules, births in Sydney, Buenos Aires, New York and London with daylight saving, and 3,000 random births. All four pillars agreed in every case. The solar terms also match the Hong Kong Observatory’s tables: 4,169 of the 4,176 terms from 1901 to 2074 fall on the same date, and the 7 that differ each fall within half an hour of midnight.
For standard time we checked the table of standard offsets, taken from the IANA time zone database, against the browser’s own clock in all 438 time zones the place search can return, every five days from 1900 to 2076: the daylight saving taken off is never less than zero or more than two hours. A second, separate program, with its own Sun positions and time zone library, gave the same four pillars for 886 births, including births in India and the United States in war time, under both clocks and both day-change rules.
What it does not do
It does not draw the luck pillars, judge the strength of the Day Master, or read the chart. It covers births from 1901 to 2074. It is offered for reflection and interest; Ba Zi is a traditional system, not a proven way to judge character or predict events.
Frequently asked questions
↳ What is my Day Master?
The heavenly stem of your day pillar, such as Yang Wood (Jia) or Yin Water (Gui). In the Ziping method it represents you, and the other seven characters are read in relation to it.
↳ Why is my Ba Zi year animal different from my Chinese zodiac animal?
Because Ba Zi starts the year at Li Chun, around 4 February, while the Chinese zodiac in everyday use starts it at the lunar new year, which from 1901 to 2074 falls between 21 January and 20 February. For a birth between the two dates the animals differ. Our Chinese zodiac tool uses the lunar new year.
↳ Do I need my exact birth time?
For the hour pillar, yes. Without a time the tool gives the year, month and day pillars, and tells you if a solar term that changes the month falls on your birthday.
↳ Should I use clock time or solar time?
Schools differ. Standard clock time is the simplest; local mean solar time follows the Sun at your exact longitude. The tool lets you choose and says when the other would change your hour or day pillar.
↳ What happens if I was born between 11 PM and midnight?
You are in the Zi hour, the first of the next day's hours. Both common rules give the hour pillar the next day's stem; they differ on whether the day pillar is the calendar day or the next day. You can choose which rule to follow.
↳ Why are the months not the lunar months?
Ba Zi uses the solar months of the Chinese calendar, which start at the solar terms, so that the month follows the seasons exactly. The lunar months, which start at each new moon, are used for festivals and birthdays; our lunar date converter gives those.