Da Yun (Major Luck Cycle) is a concept in BaZi astrology representing the fortune trends across different life stages, with each Da Yun period lasting ten years. Da Yun is derived starting from the Month Pillar: for Yang-male and Yin-female natives, it proceeds forward; for Yin-male and Yang-female natives, it proceeds backward. The elemental interactions between the Heavenly Stem and Earthly Branch of the Da Yun and the native’s chart—particularly whether they align with or oppose the chart’s favorable or unfavorable elements—determine the auspiciousness or inauspiciousness of that decade.
Da Yun is calculated starting from the Month Pillar: Yang-year males and Yin-year females follow forward progression; Yin-year males and Yang-year females follow reverse progression. Each Da Yun spans ten years. The age at which Da Yun commences (‘starting age’) is determined by the number of days between the birth date and the nearest preceding or following solar term.
For a Jia Wood Day Master with weak body constitution who favors Water and Wood, entering the Ren Zi Da Yun (Ren Water + Zi/Rat) brings the Indirect Seal (Ren Water), a Favorable/Useful Element—indicating academic and career success during that decade.