Hour-Based Qi Men: Setting the Cycle and Yin/Yang Dun
Learn how hour-based Qi Men sets the cycle from solar terms and day stems, and why Yang Dun moves forward while Yin Dun moves backward.
Updated 2026-08-21
Hour-based Qi Men uses the current hour, solar term and day stem to set up a rotating chart.
1. Solar Terms and the Three Cycles
A year has 24 solar terms, each about 15 days. Each term is divided into Upper, Middle and Lower cycles of about five days each, corresponding to different cycle numbers.
For example, Winter Solstice uses cycles 1-7-4, Minor Cold 2-8-5, Major Cold 3-9-6 for Yang Dun; Summer Solstice uses 9-3-6, Minor Heat 8-2-5, Major Heat 7-1-4 for Yin Dun.
2. Split-and-Join Method
The split-and-join method decides the current cycle from the actual moment of the solar term transition. If the term has arrived but the next cycle has not, it "splits" to the upper cycle; if the middle cycle has passed, it "joins" to the lower cycle.
This stays close to astronomical calendars, but different software may use slightly different ephemerides, so cycle numbers can differ by one.
3. Yang Dun Moves Forward, Yin Dun Moves Backward
After Winter Solstice, Yang energy rises — Yang Dun. The stems move forward through the palace numbers. After Summer Solstice, Yin energy rises — Yin Dun. The stems move backward.
This direction also governs how Zhi Fu and Zhi Shi Men travel across the chart.
4. Zhi Fu and Zhi Shi Men
Zhi Fu is the star of the current ten-day stem head's palace. Zhi Shi Men is the door of that palace. They fly through the chart according to Yang or Yin direction.
Disclaimer: Many charting methods exist. This page explains the hour-based split-and-join rotating method for reference only.
FAQ
Why do different apps show different cycle numbers?
It is usually due to different solar-term ephemerides and cycle-setting methods. Pick one method and stay consistent.
What is the intercalation method?
Intercalation adjusts accumulated differences between solar terms and stems by repeating a cycle occasionally. Split-and-join does not intercalate; it follows the real solar term directly.
Does Yin/Yang Dun affect the reading?
Yes. It determines the direction of symbol movement and the general trend: Yang Dun tends toward action and expansion, Yin Dun toward stillness and contraction.