Mastering Yang Dun and Yin Dun Structure Selection in Qimen

The Two Engines of Every Qimen Chart

Every Qimen Dun Jia chart runs on one of two structures: Yang Dun (阳遁) or Yin Dun (阴遁). Pick the wrong one and every stem, door, star, and god in your chart will be in the wrong palace. The structure is not a style choice. It is the engine that drives the rotation of the chart, and it is determined by the time of year, not the hour you are casting in.

If you are learning to cast charts, structure selection is the step after you have obtained the correct true solar time. For the complete framework, see the complete guide to casting a Qimen hour chart. This article takes a closer look at the Yang and Yin Dun mechanics and how to select the right one for any given date.

What Are Yang Dun and Yin Dun?

Yang Dun and Yin Dun describe the direction of energy flow through the year. The ancient Chinese observed that the solar year has two halves: one where energy rises outward (Yang) and one where it retreats inward (Yin). The Qimen chart encodes this by rotating its components in different directions for each half.

Yang Dun runs from the winter solstice to the summer solstice. During this period, Yang energy is growing. The days are getting longer. The chart rotates its stars, doors, and gods in the forward direction, from palace 1 through 9.

Yin Dun runs from the summer solstice to the winter solstice. During this period, Yin energy is growing. The days are getting shorter. The chart rotates its components in the reverse direction, from palace 9 back through 1.

The 72 Pentads and Structure Numbers

Within each Dun, the year is divided into 72 pentads (hou, 候), each lasting roughly 5 days. There are 36 pentads in Yang Dun and 36 in Yin Dun. Each pentad has a specific structure number from 1 to 9 for Yang Dun and 9 to 1 for Yin Dun. The structure number tells you where the lead stem sits in the Heaven Plate, and from there the rest of the chart falls into place.

The structure numbers cycle through in a specific pattern. For Yang Dun, the numbers go 1, 2, 3, 4, 5, 6, 7, 8, 9 and then repeat. For Yin Dun, they go 9, 8, 7, 6, 5, 4, 3, 2, 1 and repeat. Each structure number corresponds to a specific palace in the Luo Shu (Luoshu) grid.

Determining Which Dun to Use

The rule is simple: if the date falls between the winter solstice (around December 21) and the summer solstice (around June 21), use Yang Dun. If the date falls between the summer solstice and the winter solstice, use Yin Dun.

The exact boundary is the solstice itself. On the winter solstice, Yang Dun begins. On the summer solstice, Yin Dun begins. These dates shift slightly each year because the solar calendar is not perfectly aligned with the Gregorian calendar, so always check the exact solstice time for the year you are casting.

Step by Step: Finding the Structure Number

Once you know which Dun to use, you need the structure number for that specific date:

1. Find which of the 24 solar terms the date falls in.
2. Within that solar term, identify which of the 3 pentads the date belongs to.
3. Count from the start of the Dun to find the structure number.

For example, if you are casting a chart in early March, you are in Yang Dun (after winter solstice). The solar term is Jing Zhe (Awakening of Insects, around March 5). The first pentad of Jing Zhe is the 22nd pentad of Yang Dun, which corresponds to structure number 4 (22 mod 9 = 4, since the numbers cycle 1 through 9). Your lead stem would sit in palace 4 of the Heaven Plate.

Common Mistakes in Structure Selection

Mistake 1: Using the lunar month instead of the solar term

QMDJ uses the solar calendar, not the lunar calendar. The structure is determined by the position of the sun, not the phase of the moon. If you use a lunar calendar app to determine the date, you may get the wrong solar term and therefore the wrong structure number. Always use the 24 solar terms (jieqi) as your reference.

Mistake 2: Forgetting that the solstice is the boundary

Some students assume the Dun changes at the start of the month or at the lunar new year. It does not. The Dun changes at the exact moment of the solstice. A chart cast on June 20 is Yang Dun. A chart cast on June 22 is Yin Dun. The difference of one day flips the entire chart.

Mistake 3: Using the wrong pentad within the solar term

Each solar term has 3 pentads, and the structure number changes at each pentad boundary (roughly every 5 days). If you are near a pentad boundary, check the exact time. The structure number determines the starting palace of the lead stem, and getting it wrong shifts the entire chart.

Getting the Dun right is not about being pedantic. It is about making sure the chart speaks to the actual moment you are asking about. The Dun is the frame. Get the frame wrong and the picture is wrong.

Yang Dun vs Yin Dun in Interpretation

Beyond the mechanics of rotation, the Dun also carries interpretive meaning. A chart cast during Yang Dun has a different energy quality than one cast during Yin Dun, even if the palace placements look similar.

Yang Dun charts favor outward action, expansion, new beginnings, and visible results. If you are asking about a launch, a new partnership, or a move to a new market, a Yang Dun chart tends to support forward momentum.

Yin Dun charts favor inward work, consolidation, planning, and hidden preparation. If you are asking about strategy, research, or preparing for a future move, a Yin Dun chart tends to support reflective action. Neither is better. The question determines which is more useful.

For more on how the Eight Doors interact with these energies, see the Eight Doors complete guide and the best door and star combinations article.

Using Structure Numbers with the Heaven Plate

The structure number does more than determine rotation direction. It places the lead stem (Yonggan) in a specific palace of the Heaven Plate. From that placement, the other nine stems follow in sequence around the palaces, creating the grid that the Eight Doors and Nine Stars overlay.

This is why the structure number is so critical. It is the anchor point for the entire Heaven Plate. Move it by one palace and every stem shifts, changing the relationships between palaces and therefore the advice the chart gives. For the full distribution process, read the companion article on distributing Heaven Plate stems in the casting guide.

Tools for Structure Selection

Most modern QMDJ apps will automatically determine the Dun and structure number from the date. If you are using one, verify that it uses the 24 solar terms and not the Western calendar months. If you are doing manual calculations, a solar term calendar (jieqi table) is your essential reference. These tables list the exact dates of each solar term for each year, which lets you find the pentad and structure number.

Frequently Asked Questions

Does the lunar new year affect Yang Dun or Yin Dun?

No. QMDJ structure selection is based on the solar calendar, specifically the 24 solar terms. The lunar new year is a separate calendar system. A chart cast just before the lunar new year in late January is still Yang Dun because it falls between the winter and summer solstices.

What happens exactly on the solstice day?

The solstice is the boundary. Before the exact moment of the solstice, you use the previous Dun. After it, you switch. In practice, the solstice moment is to the minute, so if you are casting near the solstice, check the precise time and compare it to the solstice moment for that year.

Can Yang Dun and Yin Dun give the same chart?

No. The rotation direction is reversed, so the same structure number in Yang Dun and Yin Dun produces different palace placements. Even the structure numbers themselves run in opposite directions (1-9 vs 9-1), so the same date range in different halves of the year will always produce a different chart.

Is Yang Dun always better for business questions?

Not always. Yang Dun favors outward action, but some business questions are about strategy, consolidation, or waiting. For those, Yin Dun may be more appropriate. The question determines the relevance, not a blanket rule about which Dun is “better.”

Key Takeaways

• Yang Dun runs from winter solstice to summer solstice. Yin Dun runs the other half.
• The 72 pentads divide each Dun into 36 five-day periods, each with a specific structure number.
• The structure number places the lead stem in the Heaven Plate and drives the rest of the chart.
• The solar calendar, not the lunar calendar, determines which Dun to use.
• Yang Dun favors outward action. Yin Dun favors inward strategy. Both are equally useful depending on the question.

Once you can reliably select the right Dun and structure number, the next step is placing the lead star and lead door. To continue, see the full casting guide and the companion articles on door, star, and god combinations for how the structure flows into interpretation.