Four Pillars in BaZi: Year, Month, Day and Hour Columns

The four pillars in one paragraph

The four pillars are the year, month, day and hour columns of a BaZi chart. Each column carries one Heavenly Stem above one Earthly Branch, which is why four columns produce the eight characters behind the name 八字, literally eight characters. Read left to right the chart is a year, a month, a day and an hour, and there is no fifth column waiting to be found.

The day column is the one the reading works from. Its stem is the Day Master, and every other character is described by how it relates to that single stem. That is the difference between the method this site uses, 子平法, and the older system that read the year stem as the subject.

So a chart is not four independent labels. It is one anchor character plus three positions saying where that anchor sits: in which year of the cycle, in what season, and at what hour of the day.

Why four, and not three

Four columns look arbitrary until you know what came before them. The Tang-dynasty reader Li Xuzhong (李虚中) built charts from three columns, year, month and day, and read them with the year stem as the subject. Han Yu's epitaph for him is the earliest surviving description of the technique, and it describes weighing the stems and branches of a person's birth year, month and day against one another.

The fourth column arrived later, in the shift from the Five Dynasties into the early Song, and is credited to Xu Ziping (徐子平). Two changes came together: the hour column was added, and the subject moved from the year stem to the day stem. The second change is the one that matters, because it turned a chart about inherited circumstance into a chart about the person. The method still carries his name, 子平法.

The book usually named alongside him, 《渊海子平》 (Yuanhai Ziping), is a later Song compilation of that school rather than his own writing. Treat it as the text that codified the method, not as a first-hand manual.

Where each column begins

A pillar is not a calendar unit, so each one turns at its own point. Getting these wrong is the usual reason a chart comes out wrong, because an error in one column does not stay local: it changes the relationships attached to every other character.

The year column does not turn at the lunar new year. It turns at Lichun, roughly a fortnight earlier, which is why a child born in that gap belongs to one animal by the civil calendar and to the previous one by the chart. Both conventions are in everyday use: the civil new year governs official reckoning and most ordinary conversation, while the solar-term boundary governs the chart. A reading that quietly picks one without saying so is hiding a choice.

The month column does not turn on the first of the month either. It turns at the twelve jie, the markers the Hong Kong Observatory lists among the 24 solar terms: Lichun, Jingzhe, Qingming, Lixia, Mangzhong, Xiaoshu, Liqiu, Bailu, Hanlu, Lidong, Daxue and Xiaohan. The month branch follows the sun rather than the moon, which is why a lunar leap month needs no special case here.

The day column is where the schools actually disagree. Classical 子平 practice starts the new day at 23:00, when the 子 hour opens. A second convention, used by most modern chart software and by this site, keeps 23:00 to 24:00 on the current day and switches at 00:00. The two differ by exactly one day, and only for births inside that hour, so it is the first thing to check when a reading feels off by one.

How the four are read together

The four columns are not read one at a time and then added up. They are read as a hierarchy, and the hierarchy has a name: 以日为主，月令为提纲, take the day as the subject and the month as the outline.

In practice that is three passes. First the Day Master gives you a subject: one stem, one element, one polarity. Then the month branch gives you the season that subject was born into, and whether it is strong or weak there. Only then do the remaining characters get their names, because the ten gods are relationships to the day stem rather than fixed labels sitting on the branches.

The other two columns carry positions the reading leans on. The year column is the earliest layer, and the one the older three-column method treated as the subject. The hour column is fixed last and sits last in the arc of a life. Their branches also point at particular people, the day branch to a partner and the hour branch to children, which is a convention of the system rather than a finding about anyone's family.

What the four pillars do not say

Four columns are a structure, and structure is not a forecast. Nothing in the eight characters names a year in which something happens; that comes from the luck cycles and the annual pillars stacked on top, which is a separate calculation with its own assumptions. And the four columns are one member of a larger family: what Chinese astrology covers.

There are also gaps a birth date cannot close. If the hour is unknown, one whole column is missing, and what still holds without a birth time covers what survives. If the birth hour sits near a boundary, a few minutes move the hour branch, and the true solar time correction depends on how far the birthplace sits from the standard meridian. This site applies a longitude correction before casting the chart, so the further east or west you were born, the more the clock time shifted.

And a chart does not separate two people born at the same moment in the same place. Twins share four pillars. Whatever else the system is describing, it is not the whole of a life.

Reading your own four pillars

You need a full birth date, a birth time to the hour, and a birthplace. With those, the chart tool lays out all four columns, the day master and the ten gods in one pass; the zodiac calculator is the lighter version if you only want the animal and its element.

One note on names, because it costs people real time. English writing calls these four positions pillars, columns, and the four pillars of destiny, and all three mean 四柱. A different word is a different vocabulary, not a different system.