Yang YunSong's SanHe read the landscape with extraordinary care: where the dragon runs, where the spot sits, which orientation is true. But it left a second question quietly unanswered. It could tell you where energy was favorable. It could not fully tell you when. A house that flourishes in one era can struggle in the next without a single wall being moved. Answering that, folding time into feng shui, is the work of the SanYuan tradition and its crown jewel, XuanKong.
The Idea of Cycles
SanYuan means "three cycles." The tradition divides time into a repeating structure, three cycles of three periods each, nine periods in all, spanning a hundred and eighty years. Each period carries a different quality of energy, and the sectors of a home rise and fall in fortune as the periods turn. This is the crucial claim: energy is not a fixed property of a place. It is a relationship between a place and a moment. The very same room can be a room of prosperity in one period and a room of difficulty in the next.
We are, right now, in the ninth of those periods. This is exactly why the timeline of Classical Feng Shui runs "from the Yellow River to Period 9", the periods are not history, they are the live clock the system still runs on.
Knowledge Nearly Lost
The time-based methods had roots reaching back to Song-dynasty masters, but the thread was fragile and nearly snapped. The tradition tells of knowledge preserved by a single daughter when a master's line failed, of texts hidden and rediscovered generations later. Esoteric knowledge in the classical world was always one careless generation away from vanishing, which is part of why it was guarded so jealously, and why its eventual writing-down mattered so much.
Jiang Dahong, the Great Systematizer
The figure who gathered these threads into a coherent, transmissible system was Jiang DaHong, working across the Ming-to-Qing transition. His work, above all the treatise remembered as DiLi BianZheng, "discerning the truth of earth study," became the doctrinal backbone of SanYuan XuanKong. He is the reason the time-based tradition has a spine at all.
He was also famously, almost painfully, careful. The tradition describes decades of hesitation before he would transmit the full method, testing it against real cases, guarding it against misuse. When he finally did pass it on, he is said to have distributed pieces among different disciples rather than giving any one person the whole, a decision that protected the knowledge but also seeded centuries of schism, as later practitioners argued over who held the genuine transmission. It is a very human story: the same caution that preserved the truth also fractured it.
What “XuanKong” Actually Means
XuanKong is often translated as "time and space," and that phrase is the whole idea in two words. A SanHe reading asks, in effect, "is this orientation good?" A XuanKong reading asks, "is this orientation good now, in this period, and what will it become when the period turns?" It marries the compass direction of a home to the moving clock of the cycles. Direction is the space. Period is the time. Read together, they describe the living, changing energy of a specific home at a specific moment in history.
Why Your Reading Has a Date
This is the reason a serious analysis of your home is never timeless. It is anchored to now, to the current period, to this year's moving energy. The chart we calculate for your rooms is a XuanKong chart, and it exists because Jiang DaHong refused to let the tradition treat a house as a fixed object. A home, like the people in it, is moving through time. Reading it well means reading the moment as carefully as the map.