section_path: Sexagenary system
section_name: Sexagenary system
paragraph_text: Sexagenary system
  
  Several coding systems are used to avoid ambiguity. The Heavenly Stems is a decimal system. The Earthly Branches, a duodecimal system, mark dual hours (時; 时; shí or 時辰; 时辰; shíchen) and climatic terms. The 12 characters progress from the first day with the same branch as the month (first Yín day (寅 日) of Zhēngyuè; first Mǎo day (卯 日) of Èryuè), and count the days of the month.
  
  Years, months, days of the month and hours could traditionally numbered by the terminology of the Chinese sexagenary cycle.
  
  The stem-branches is a sexagesimal system. The Heavenly Stems and Earthly Branches make up 60 stem-branches. The stem branches mark days and years. The five Wu Xing elements are assigned to each stem, branch, or stem branch.
  
  For example, the year from 12 February 2021 to 31 January 2022 was a Xīnchǒu year (辛丑 年) of 12 months or 354 days. The 60 stem-branches have been used to mark the year since the Shang dynasty (1600 BCE – 1046 BCE). Astrologers knew that the orbital period of Jupiter is about 12×361 = 4332 days, which they divided into 12 years (歲; 岁; suì) of 361 days each. The stem-branches system solved the era system's problem of unequal reign lengths.
  
  Current naming conventions use numbers as the month names, although each month is also associated with one of the twelve Earthly Branches. Correspondences with Gregorian dates are approximate and should be used with caution. Many years have intercalary months.
  
  Historically, Chinese had days of the month numbered with the 60 stem-branches:
  
  天聖元年… 二月 … 丁 巳，奉安太祖、太宗御容于南京鴻慶宮. Tiānshèng 1st year… Èryuè … Dīngsì, the emperor's funeral was at his temple, and the imperial portrait was installed in Nanjing's Hongqing Palace.
  
  Fortune-tellers identify the heavenly stem and earthly branch corresponding to a particular day in the month, and those corresponding to its month, and those to its year, to determine the Four Pillars of Destiny associated with it, for which the Tung Shing, also referred to as the Chinese Almanac of the year, or the Huangli, and containing the essential information concerning Chinese astrology, is the most convenient publication to consult. Days rotate through a sexagenary cycle marked by coordination between heavenly stems and earthly branches, hence the referral to the Four Pillars of Destiny as, "Bazi", or " Birth Time Eight Characters ", with each pillar consisting of a character for its corresponding heavenly stem, and another for its earthly branch. Since Huangli days are sexagenaric, their order is quite independent of their numeric order in each month, and of their numeric order within a week (referred to as True Animals in relation to the Chinese zodiac). Therefore, it does require painstaking calculation for one to arrive at the Four Pillars of Destiny of a particular given date, which rarely outpaces the convenience of simply consulting the Huangli by looking up its Gregorian date.
  
  The Tang dynasty used the Earthly Branches to mark the months from December 761 to May 762. Over this period, the year began with the winter solstice.
  
  China has used the Western hour-minute-second system to divide the day since the Qing dynasty. Several systems were in use historically; systems using multiples of twelve and ten were popular, since they could be easily counted and aligned with the Heavenly Stems and Earthly Branches.