Sixty Month Pillars: Month Boundaries by Twelve Solar Terms

The sixty 月柱 are the sixty possible combinations of a heavenly stem and an earthly branch that can occupy the month pillar in a bazi chart. The month pillar is one of the four pillars in Chinese calendrical and natal practice, and its sixty forms are generated by pairing the ten heavenly stems with the twelve earthly branches in the sexagenary cycle. In practice, only twelve month branches occur in any solar year, but the stem attached to each month branch changes according to the year stem, producing the full set of sixty month pillars across the cycle.

月柱与月令的关系

The month pillar is inseparable from the concept of 月令, the seasonal command that governs the month. In Chinese calendrical usage, the year is divided into twelve solar months, and each solar month is defined by one of the twelve earthly branches. The month pillar therefore expresses both the heavenly stem and the earthly branch of the month in which a person is born or an event occurs. The earthly branch of the month pillar is the 月令 branch, and it carries the strongest seasonal influence in a chart. Because the month pillar marks the seasonal position of the sun along the ecliptic, it is taken as the primary indicator of the prevailing qi at the time of birth. The twelve month branches run in fixed order from 寅 to 丑, beginning with the first month of the solar year.

节气换月而非农历换月

The month pillar changes at the twelve 节, not at the beginning of a lunar month. The twelve 节 are 立春，惊蛰，清明，立夏，芒种，小暑，立秋，白露，寒露，立冬，大雪, and 小寒. These are the solar terms that mark the entry into each solar month. The intermediary solar terms such as 雨水，春分, and 谷雨 are 气, not 节, and they do not determine the change of the month pillar. Only the 节 serve as month boundaries.

The exact moment of a 节 is fixed by astronomical observation and is given to the minute. If two people are born on the same calendar day but on opposite sides of the moment of a 节, their month pillars will differ. This is a direct consequence of using the solar term, rather than the civil date or the lunar date, as the boundary of the month pillar. The minute-level precision of the 节 means that even a short interval across a boundary can change the month branch and, with it, the month pillar.

六十月柱与出生月份的对应

The lunar new year does not coincide with the beginning of the 寅 month. A person born before the moment of 立春 may already be in the first lunar month by the traditional calendar, but the month pillar still belongs to the twelfth month of the previous year. The first lunar month corresponds to the 寅 month only in the solar framework, and the 寅 month runs from 立春 to 惊蛰. Because the solar month is tied to the sun’s position rather than to the phases of the moon, a difference of one day across the 立春 boundary can mean a difference of one month pillar. The sixty month pillars thus correspond to birth months only when the birth month is understood as a solar month beginning at a 节.

月柱在六亲取象里的位置

Within the four pillars, each pillar is assigned a role in the traditional division of the life course and of relational imagery. The year pillar governs early life and the ancestral line. The month pillar governs youth and the career or social environment. The day pillar governs the self and the marriage palace. The hour pillar governs late life and outward expression. In this scheme, the month pillar is the pillar of the developmental years and of the surrounding institutional or professional setting. It is not used as the primary indicator of the self, but as the field in which the day master operates during the formative and working years.

月柱条目不单独成断

The month pillar is not read in isolation. Its meaning is derived from the combination of the heavenly stem and earthly branch, and from the hidden stems stored within the branch. Each month branch contains a principal qi, a central qi, and a residual qi, as traditionally assigned. The 子 branch is an exception in that it purely stores 壬 water, and its qi is considered concentrated. The 午 month stores 丁 fire as its principal qi and 己 earth as its central qi. The four storage branches 辰，戌，丑, and 未 hold the most complex hidden stem arrangements among the twelve branches.

The 寅 branch stores 甲 wood as its principal qi, 丙 fire as its central qi, and 戊 earth as its residual qi. In the sexagenary cycle, 甲寅 is the fifty-first combination, and its nayin is 大溪水, or great stream water. The 申 month is the first month of autumn, storing 庚 metal, 壬 water, and 戊 earth. Its beginning point is 立秋, when the sun’s ecliptic longitude reaches 135 degrees. 庚申 is a stem-and-branch combination in which both the stem and the branch are of the same elemental character, and it is described as a pure yang metal pillar.

The month branch also enters traditional methods for locating 桃花, or the peach blossom indicator. The usual method derives 桃花 from the three-harmony frame of either the year branch or the day branch: 申子辰 meet at 酉，寅午戌 meet at 卯，亥卯未 meet at 子, and 巳酉丑 meet at 午. When the resulting branch falls in the month position, it is called a month-pillar peach blossom. 桃花 is also referred to as 咸池; the checking method is the same, and only the name differs. The presence of 桃花 in the month pillar is a positional matter within the chart and does not by itself determine a fixed outcome. The month pillar entry, whether considered through its hidden stems, its nayin, or its peach blossom position, is one component within the larger four-pillar structure and is not separately decisive.