Chart Calculation and Solar Terms

ICore principles and calendar foundations

IIPrecise boundaries of the four pillars

• Year-pillar boundary: The year changes at the exact instant of Li Chun, the Beginning of Spring. If lunar New Year has passed but Li Chun has not, the birth still belongs to the preceding BaZi year. The zodiac animal follows the same rule here.
• Month-pillar boundary: Months change at the twelve jie boundaries among the twenty-four solar terms, rather than at the twelve intervening principal terms, or zhongqi.
  • Yin, month 1: Li Chun to before Jing Zhe.
  • Mao, month 2: Jing Zhe to before Qing Ming.
  • Chen, month 3: Qing Ming to before Li Xia.
  • Si, month 4: Li Xia to before Mang Zhong.
  • Wu, month 5: Mang Zhong to before Xiao Shu.
  • Wei, month 6: Xiao Shu to before Li Qiu.
  • Shen, month 7: Li Qiu to before Bai Lu.
  • You, month 8: Bai Lu to before Han Lu.
  • Xu, month 9: Han Lu to before Li Dong.
  • Hai, month 10: Li Dong to before Da Xue.
  • Zi, month 11: Da Xue to before Xiao Han.
  • Chou, month 12: Xiao Han to before Li Chun.

IIITen-year cycles and annual influences

“The natal chart is the vehicle; the cycles are the road.”

• Ten-year cycles begin from the month pillar. Men born in yang years and women born in yin years proceed forwards; the reverse combinations proceed backwards. Each cycle represents the broader setting and basic tone of a decade.
• An annual influence is the stem–branch pair of the current year, a time coordinate shared by everyone. The stems and branches of cycles and years interact directly with the natal four pillars through generation, restraint and transformation, producing the favorable or adverse developments considered in the reading.
• Timing analysis starts by establishing the exact Li Chun boundary and the dates on which ten-year cycles change.

IVThe solar calendar and true solar time

In this approach, chart calculation uses solar terms for the date and true solar time for the hour pillar.

• Earth’s rotation and orbit mean that solar time varies by longitude. Beijing time is a standardized civil time. This method converts it to local mean solar time at the birthplace, then applies the equation of time to obtain apparent, or true, solar time, helping prevent an incorrect hour-pillar boundary crossing.

Growth follows the Sun. BaZi’s stem–branch calendar is essentially solar: aligning time and place with astronomical motion provides the framework for mapping the seasonal qualities of Wood, Fire, Earth, Metal and Water.