The Four Pillars: Year, Month, Day, Hour

A BaZi chart consists of four pillars. Each pillar is a pair of characters: a Heavenly Stem on top (one of ten) and an Earthly Branch below (one of twelve). The pillars are named after units of time — the year, month, day and hour of birth — and together they give the eight characters from which the system takes its name. If you are not yet familiar with the basics, start with What Is BaZi.

How a pillar is built

The ten Heavenly Stems are the five elements in two polarities: Jia and Yi are Wood, Bing and Ding are Fire, Wu and Ji are Earth, Geng and Xin are Metal, Ren and Gui are Water. The first in each pair is Yang, the second Yin. The twelve Earthly Branches — Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, Hai — also belong to elements, and in folk tradition they are linked to animals: Rat, Ox, Tiger and so on. At Bazi.uz the animals serve as an illustration of the branches, not as the basis of interpretation.

The stem and branch in a pillar are not arbitrary: they follow the sixty-step cycle, in which Yang stems pair only with Yang branches and Yin stems only with Yin branches. So a pillar 甲子 (Jia-Zi) exists, but 甲丑 does not.

The year pillar

The year pillar shows the broadest context: the environment, the generation, what a person "enters" life with. In classical interpretation it is associated with ancestors and the early years. It is calculated using the sixty-step cycle, but the year boundary is not 1 January — it is the moment of Li Chun (Start of Spring), around 4 February. If you were born in January or in the first days of February, your year pillar belongs to the previous year.

The month pillar

The month pillar is one of the weightiest in the chart. Its branch sets the season of birth, and the season determines how strong the Day Master is: Wood born in spring is stronger than Wood born in autumn. That is why the season is the main factor when assessing the strength of the Day Master. The month branch is determined by the solar seasons: the Yin month begins at Li Chun, the Mao month at Jingzhe, and so on — twelve nodes in all. The month stem is derived from the year stem using the "five tigers" rule: for example, in Jia and Ji years the Yin month begins with the stem Bing.

In interpretation the month pillar often describes a person's social style, their working environment and how they build relationships within a group.

The day pillar

The day pillar is the centre of the chart. Its stem is called the Day Master and represents the person themselves: all of the Ten Gods are determined in relation to it. See the article on the Day Master for details. The day branch is called the "spouse palace": it is where the theme of close relationships and personal space is examined.

The day pillar is calculated from the continuous sixty-day cycle. The day changes at 00:00. In the Bazi.uz methodology the Zi hour (23:00–01:00) is split: 23:00–23:59 is the "late Zi" with the pillar of the current day, while 00:00–00:59 is the "early Zi" with the pillar of the new day. Some schools move the change of day to 23:00; this is a configurable rule, and by default we use the split.

The hour pillar

The hour pillar describes inner intentions, the later years and what a person passes on — ideas, projects, students. The hour branch is determined by two-hour blocks: Zi is 23–01, Chou 01–03, Yin 03–05, and so on up to Hai at 21–23. The time used is true solar time, that is, adjusted for the longitude of the birthplace. The hour stem is derived from the day stem using the "five rats" rule: for example, on Jia and Ji days the Zi hour begins with the stem Jia.

The hour pillar is the one that most often differs between calculators. If the time of birth is close to the boundary of a two-hour block, a difference of twenty to thirty minutes changes the pillar. More on this in the article on true solar time. If the time is unknown, the hour pillar is not built at all — see A Chart Without a Birth Time.

How the pillars work together

The pillars are not read in isolation. The strength of the Day Master depends on the season (the month pillar), on how many stems and Hidden Stems of its own element and of its resource element appear in the chart, and on whether it has roots in the branches. Branches of different pillars can clash: six pairs — Zi and Wu, Chou and Wei, Yin and Shen, Mao and You, Chen and Xu, Si and Hai — are marked in the methodology as clashes and are taken into account in a reading as tension between the corresponding areas.

The usual reading order is: first the Day Master and its image, then the season and strength, then how the Ten Gods are distributed across the pillars, and finally the periods — Luck Pillars and years.

In short

• Year — the environment and the broadest context; the year boundary is Li Chun.
• Month — the season, the main factor in the Day Master's strength; social style.
• Day — the person themselves (the Day Master) and the area of close relationships.
• Hour — intentions and the later years; requires an accurate time of birth.

An example reading by pillar

Take the example chart: hour 丙寅, day 甲申, month 辛巳, year 庚午. The Day Master is 甲, Yang Wood, the "great tree". It is born in the 巳 month — the season of Fire, which draws strength away from Wood, so the chart is assessed as weak. The year and month stems are 庚 and 辛, Metal: for Wood this is "authority", external demands and boundaries. In the hour pillar stands 丙, Yang Fire — the Eating God, self-expression; its branch 寅 hides 甲, the same element as the Day Master, which is a root the chart can rely on. The day branch 申 and the hour branch 寅 stand opposite each other — one of the six clashes — and 申 hides Geng, another Seven Killings.

Even such a short pass through the pillars is enough to see the structure: many external demands (Metal), a strong outflow of energy (Fire) and little direct support. Hence the favourable elements here are Water and Wood.