CALENDARS & SYMBOLS · 6 MIN READ

Heavenly Stems and Earthly Branches, Explained

A beginner's guide to the ten Heavenly Stems, twelve Earthly Branches, and the cycle they form together.

The Heavenly Stems (天干, tiāngān) and Earthly Branches (地支, dìzhī) are two ordered sets of signs used in traditional Chinese calendrical notation. There are ten stems and twelve branches. Pairing them in sequence produces sixty combinations, often called the sexagenary or stem-branch cycle.

The names “Heavenly” and “Earthly” are conventional translations. They do not mean that each sign is a modern astronomical object or a physical force. In many systems, the signs are associated with yin-yang, the Five Elements, directions, seasons, and other categories. Those correspondences depend on the system and should not be mixed without explanation.

The ten stems#

The stems are Jia (甲, jiǎ), Yi (乙, yǐ), Bing (丙, bǐng), Ding (丁, dīng), Wu (戊, wù), Ji (己, jǐ), Geng (庚, gēng), Xin (辛, xīn), Ren (壬, rén), and Gui (癸, guǐ). Each is assigned yin or yang and one of the Five Elements in common calendrical and divination systems. A stem can mark a position in a cycle; it does not have one universal personality meaning in every context.

The twelve branches#

The branches are Zi (子, zǐ), Chou (丑, chǒu), Yin (寅, yín), Mao (卯, mǎo), Chen (辰, chén), Si (巳, sì), Wu (午, wǔ), Wei (未, wèi), Shen (申, shēn), You (酉, yǒu), Xu (戌, xū), and Hai (亥, hài). They are also used to mark the twelve double-hours and are associated with the twelve zodiac animals in popular explanations. The animal associations are a helpful mnemonic, but they do not replace the branch name or its role in a calculation.

Why the combined cycle has sixty pairs#

One stem advances with each step through ten positions, and one branch advances through twelve. The sequence continues until both cycles return to their starting positions; that takes sixty steps. The first pair is Jiazi (甲子), and the sixtieth is Guihai (癸亥). Because not every possible stem-branch combination occurs, it is important to preserve the order rather than choose any stem and branch at random.

The cycle can label years, months, days, and hours. BaZi uses four such labels to represent a birth moment, but the calendar rules for boundaries matter. A year or month pillar may change at a solar-term boundary, while conventions for the day boundary can differ. See Solar Terms and the BaZi Calendar.

A useful way to learn#

First memorize the ordered lists. Then practice moving one step at a time through the paired cycle. When comparing two calendars or calculators, keep the date, time zone, daylight-saving rule, and boundary conventions identical. A mismatch near a boundary can produce different results even if the underlying cycle is being applied consistently.

For related terms, see the glossary entries for Heavenly Stems, Earthly Branches, and the Chinese sexagenary cycle.