The 60 Day Pillars: Stems and Branches in BaZi

The sixty day pillars, or 六十日柱, are the sixty combinations of the ten heavenly stems and twelve earthly branches that form the sexagenary cycle. In bazi practice they provide the day column of the four pillars. Each day pillar consists of one heavenly stem above and one earthly branch below, and the pair recurs in a fixed sequence through the calendar.

日柱在整张盘里的位置

The four pillars are the year, month, day, and hour columns. Among them, the day pillar is the only column that is independent of the solar terms. The year pillar changes at the beginning of spring, and the month pillar changes at the twelve major solar terms. The day pillar, by contrast, is obtained from the continuous sixty-day cycle of the sexagenary day order; the change of a solar term does not interrupt that day sequence. This makes the day pillar structurally different from the year and month pillars, because it is tied to the sexagenary day count rather than to the solar-term calendar.

In a full chart, the heavenly stem of the day pillar is called the day master or day yuan. The ten-god system is built around this stem. The earthly branch of the day pillar is the spouse palace. For this reason, if the day pillar is identified incorrectly, the day master and the spouse palace are both wrong at the same time. The day pillar therefore occupies a central reference position in the chart: it supplies the self-reference point for the ten gods, and it also supplies the branch that is read as the spouse palace.

六十日柱的排列方式

The sixty jiazi combinations are formed by pairing the ten heavenly stems with the twelve earthly branches. A yang stem pairs only with a yang branch, and a yin stem pairs only with a yin branch. This rule produces sixty combinations rather than one hundred and twenty. The sequence begins with 甲子 and continues through the sixty possible pairs before returning to 甲子.

Because the ten stems and twelve branches are both cycled together, the same stem appears with six different branches across the full sixty-pillar set, and the same branch appears with five different stems. Each day pillar is therefore a specific stem-branch pair, such as 庚申 or 甲子. The fixed order of the sixty pairs is the same order used for years, months, days, and hours in the sexagenary calendar, but the day pillar applies that order to the continuous day count.

日支所承载的配偶宫

The earthly branch of the day pillar is read as the spouse palace. This is a positional assignment rather than a statement about any particular spouse. In bazi analysis, the branch beneath the day stem is the palace associated with marriage and the spouse, just as the year branch is associated with ancestors and the hour branch with children or later life. The day branch is not interpreted in isolation; it is read together with the day stem, the other three branches, and the interactions among the stems and branches.

Because the day branch is the spouse palace, any error in the day pillar affects that palace directly. If the day pillar is shifted by one position, the spouse palace branch changes, and the day master stem may also change. This is why the day pillar is treated as a load-bearing element in chart construction. It does not by itself determine marital fortune, but it supplies the palace through which marriage-related readings are made.

同一日干配不同地支

The same day stem can combine with different earthly branches across the sixty-day cycle. A given heavenly stem appears in six day pillars. For example, the stem 庚 appears with six different branches, one of which is 申. In the 庚申 pillar, the stem 庚 metal and the branch 申 metal are both yang metal; 申 is the lin guan position of 庚, and there is no clash or control between the stem and branch.

A different example is 甲子, the first of the sixty jiazi. In 甲子, the day branch 子 water produces the day stem 甲 wood. These two examples show that the same day stem can sit on very different branches, with different stem-branch relationships. The branch changes the condition of the day stem, and it also changes the spouse palace. The same day master therefore does not carry the same reading across all six possible day pillars; the branch beneath it matters.

日柱条目的读法与限度

A day pillar entry states the heavenly stem and earthly branch of the day. It can establish the day master and the day branch, and it can describe the fixed stem-branch relationship within that pillar. What it cannot do is yield a complete judgment about career success or marital fortune on its own. The day pillar is one column among four. It must be read together with the year, month, and hour pillars, and with the larger structure of the chart.

The site engine converts a Gregorian calendar date into a day pillar by using the Julian day number. It takes the Julian day number of that date, subtracts the Julian day number of a fixed base date, and takes the remainder modulo sixty. The remainder gives the position of that date in the sixty-jiazi sequence. This is a mechanical conversion from calendar date to cycle position.

For births at the boundary of a day, the site follows the late zi hour convention. A person born between 23:00 and 23:59 is assigned the day pillar of the following day, while the hour pillar is still calculated from the actual birth clock time. This means the day pillar and hour pillar can cross the midnight line differently. Hand calculation of the year, month, and hour pillars can be done with standard formulas, but the day pillar has no such formula; it must be looked up in a table or calculated by a program.

When different tools give different day pillars for the same date, the disagreement usually comes from one of two places: the assignment of the zi hour, or the time zone used for the date. It does not usually come from a difference in the sixty-jiazi day sequence itself. The sequence is fixed; disputes arise at the boundary conventions that map a local birth time onto that sequence.