U+620A CJK Unified Ideo­graph-​620A

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The ten Heavenly Stems (or Celestial Stems) are a system of ordinals indigenous to China and used throughout East Asia, first attested c. 1250 BCE during the Shang dynasty as the names of the ten days of the week. They were also used in Shang-era rituals in the names of dead family members, who were offered sacrifices on the corresponding day of the Shang week. Stems are no longer used as names for the days of the week, but have acquired many other uses. Most prominently, they have been used in conjunction with the associated set of twelve Earthly Branches in the compound sexagenary cycle, an important feature of historical Chinese calendars.