Tian Ji's Place in the Zi Wei Series

Tian Ji is the second of the six stars making up the Zi Wei series, the group of major stars whose palace positions across a birth chart's twelve palaces are fixed together as soon as Zi Wei's own position has been calculated from the birth date and hour, rather than each of the six being placed by an independent calculation of its own. This lookup structure means Tian Ji's palace in any given chart stands in a permanently fixed relationship to Zi Wei's, the same offset holding true across every chart the system produces, a mechanical regularity that mirrors the star's own name and character rather neatly, since Tian Ji itself is read as the star of mechanism and calculated motion. The six member Zi Wei series sits alongside the eight member Tian Fu series as the two founding calculations behind the whole natal chart, and only once both a chart's Zi Wei and Tian Fu positions are known can the remaining twelve stars of both series be read off the fixed offset tables the tradition preserves.

Ho Peng Yoke's treatment of the system describes this two series structure as one of Zi Wei Dou Shu's most distinctive features among Chinese fate calculation methods, setting it apart from Ba Zi, the Four Pillars of Destiny, which builds its reading from the birth data's own stems and branches rather than from a pair of seeded star positions.