What the ten-year luck pillars are

A BaZi chart is fixed at birth, but the tradition reads it against time. The main cycle is the luck pillars (大運): a sequence of sign pairs, one per ten years, taken from the month pillar and running forward or backward through the sixty-step cycle. Each pillar is the background against which the chart is read for a decade.

Where they come from

The example throughout these materials is a woman born on 21 March 1990 at 10:30 in Madrid; the chart was calculated by the BaziArt engine with true solar time. Nothing about this chart is special; it was chosen because it illustrates several of the rules described here.

The direction follows the polarity of the year stem and the gender: forward for a yang year and a man or a yin year and a woman, backward otherwise. The year stem here is 庚, a yang stem, and the person is a woman, so the pillars run backward from the month pillar 己卯.

The first pillar is the one after (or before) the month pillar in the cycle, and each next one steps once more in the same direction. Nothing in the sequence is chosen: once the month pillar, the gender and the year's polarity are known, the whole sequence follows.

The start age

The start age comes from the distance in days between the moment of birth and the nearest sectional solar term (jié, the term that opens a month, not the mid-term): the next one when counting forward, the previous one when counting backward. Three days count as one year, one day as four months. In the example the first pillar starts at age 5, on 31 May 1995: the distance from the birth to the previous solar term, converted at three days per year.

Because the distance depends on the hour of birth, an unknown hour gives a range of start ages rather than one number; the app shows the range and does not pretend to precision it does not have.

How a pillar is read

In this system a luck pillar is read as the chart itself: its stem and branch take a ten-god relation to the Day Master, and the engine classes the elements the pillar adds as supporting the Day Master or as drawing on it. The reading is a rule-based rating, not a statement about what will happen: it says “in this decade the chart holds more of what supports its Day Master” and shows why.

The app also reads the year against the chart (the annual pillar) and, in the planner, the month and the day. The luck pillar is the slowest of these layers and the first one practitioners look at.

In the app

The chart screen shows all luck pillars with their start years, marks the current one, and explains each with “why I see this”. The calculator on this site shows the start age and the current pillar; the full sequence and its reading are in the app. The rule and its thresholds are on the calculation method page, and the term is explained in the library.