What is 'Da Yun' (Major Luck) in Four-Pillar astrology?

Da Yun (Major Luck) is the principal long-term timing system in BaZi. It maps life into successive ten-year cycles that change how the natal elements interact—essentially the climate in which the chart plays out.

How Da Yun is calculated:
Starting from the month pillar, the sequence of ten-year luck pillars is arranged either forward or backward according to gender and stem polarity (commonly summarized as 'yang male/ying female go forward; yin male/yang female go backward') and the official 'starting age' is computed by counting days to the next or previous solar term.

Meaning and use:
• Ten-year rhythm: Each Da Yun lasts roughly ten years and defines a broad phase—early, middle and late life patterns.
• Interplay with natal chart: A luck pillar is judged by whether it strengthens the day-master (a favorable luck) or brings in a harmful element. A beneficial Da Yun can unlock potential; an unfavorable one can produce setbacks.
• Timing nuances: The first half of a Da Yun emphasizes the Heavenly Stem’s effect; the second half tends to show the Earthly Branch’s influence. Da Yun interacts with annual years (liunian), which are the specific weather within each decade.
• Triggering chart potential: Da Yun can activate latent configurations or clash with stored energies, producing events corresponding to wealth, career, marriage, or illness.
By studying Da Yun you can anticipate windows of opportunity and challenge and plan accordingly—this is why BaZi is often used for long-term life planning.