Da Yun (Ten-Year Luck Cycle) in Four Pillars

Da Yun represents the long-term luck cycles in a person's life, complementing the natal chart (Ba Zi). It acts as 'postnatal energy' adjusting the 'prenatal fate', influencing opportunities, challenges, and timing.

**Calculation:**
- Derived from the Month Pillar; males born in Yang years and females in Yin years follow forward sequence, others reverse. Each step represents 10 years.
- Starting age is calculated from birth to the next or previous solar term, converting days into years (3 days = 1 year, 1 day = 4 months, 1 double-hour = 10 days).

**Principle & Effect:**
- Ten-year cycles depict life rhythm (childhood, youth, middle age, old age). Favorable elements in Da Yun (Use Stars) enhance abilities and success; unfavorable elements (Avoid Stars) bring challenges.
- Heavenly Stem emphasizes external, active, societal influences; Earthly Branch emphasizes internal, stable, foundational matters.
- Da Yun can activate latent potentials in the natal chart, affecting the Ten Gods and other structures, guiding strategic timing for career, wealth, health, and relationships.