What This Is
A two-hour window touching the root of the ten-year arc. The 大运 governs a decade of a life and sets its broad course; when the hourly branch clashes the current decade's branch, this is 流时大运冲 — the finest-scale interaction between the timing layers, a brief touch on the long cycle's foundation. 子平真诠 gives the principle: when a transit meets a clash, there must be a turning point. At this scale, the turning point registers within a single 时辰.
It is a daily occurrence and usually imperceptible. Its salience concentrates entirely at the decade's transition phases.
When It Fires
It fires when the hourly branch forms a 六冲 with the current decade branch — once each day, the same two-hour window. It carries weight chiefly during decade transitions: the months around entering or leaving a 大运, when the long cycle is changing and even a fine-scale touch on its root can mark a decision's moment.
What It Changes
It surfaces, at most, a precise interval tied to the decade's direction. Because the decade governs the long themes of career, residence, and life-phase, a clash to its root brings — when it brings anything — a brief window where a decade-relevant matter stirs at a specific hour. Most days this is below notice; the configuration's whole significance is timing, not force.
Near a decade pivot, the same hourly clash can mark the exact interval within a transition window when a decision becomes possible or a shift announces itself — the long cycle's change finding its hour.
How To Read It
Read it by where the decade stands and at the proper scale. Mid-decade in a stable stretch, the hourly clash is negligible — a fine ripple on the long root, easily passed. At a decade's edge, the same window gains relevance: classical 择时 uses it to identify the disadvantageous hours for decade-relevant decisions, and to find the intervals when a transition can be acted on cleanly.
Direction follows the chart — a clash weakening a favorable decade's support reads as a small unfavorable window, while one opening room in an unfavorable decade reads as a small relief. Never flat: the hourly decade-clash is weighed against whether the decade serves the chart and how near its turning points the hour falls, and it is always read as the finest of triggers.
Where This Shows Up
A window of this kind is, in ordinary stretches, barely felt — a faint touch on the long themes of trajectory and phase, passing without trace. Its use is in the timing of consequential, decade-relevant decisions: identifying which two-hour intervals to avoid or to favor when a major shift is in motion.
Near a decade's transition, the texture sharpens into precision: the hourly clash can be the exact interval when a long-building change is best acted on, or best left alone. The register is always the decade's broad matters, sounded at the smallest possible scale — a tool for choosing the moment, most meaningful at the turns of the long cycle and quiet in between.