According to I-ching, ancient Chinese began to count the years by matching the Chinese zodiac and Heavenly Stems & Earthly Branches since the 1st century. The years with the same earthly branch match the same zodiac, like Jiashen, Bingshen, Wushen, and Gengshen are all monkey (earthly branch being Shen) years.

Since the Han Dynasty, ancient Chinese people divided a day time into twelve parts based on sunrise. They matched those twelve parts with twelve earthly branches, which also match the twelve Chinese zodiacs. These three counting methods make up the unique ancient Chinese time.

1.What are the twelve earthly branches? Which zodiacs do they match?

Zi(子): 23:00 -1:00

Zi in the earthly branch means to nurture. The Yangqi begins to gather and provide nutrition to the worldly things.
Zodiac: Rat
Rats are quite active at this time. They will hang around and make sure there are no predators. The rat people are more likely to be careful when they seek fortune.
Nature: Yang
Element: Water
Orientation: North

Chou（丑）: 01:00 - 03:00

It's a time when the Yangqi is still in the air and yet to be descended.
Zodiac: Ox
The ox ruminates to digest further the hays it had in the day time. The ox people are considered slow in action but more potent in the long run.
Nature: Yin
Element: Earth
Orientation: Center

Yin(寅): 03:00 - 05:00

The Yangqi is gathered together and fertilizing everything.
Zodiac: Tiger
At this time, tigers will go downhills hunting majestically. The tiger people are willing to admit their defeat. They will do everything in their power to pursue one course once they decide.
Nature: Yang
Element: Wood
Orientation: East

Mao(卯): 05:00 - 07:00

Everything begins to thrive upon the sunrise.
Zodiac: Rabbit
Rabbits are most active at the time. They will bounce around for food, which is quite interesting, considering how timid they are at other times. The rabbit people are often quiet outside but very active inside.
Nature: Yin
Element: Wood
Orientation: East

Chen(辰): 07:00 - 09:00

Things begin to change drastically and thrive more.
Zodiac: Dragon
At this time, the cold air will rise and become a cloud. In Chinese culture, there is only one animal that can fly, the dragon. The dragon people are considered ambitious no matter the circumstances.
Nature: Yang
Element: Earth
Orientation: Center

Si (巳): 09:00 - 11:00

Yangqi begins to reach its utmost and providing the best elements for earthly things.
Zodiac: Snake
The ice-cool snakes become active as the earth becomes warmer. The snake people may seem to be calm and unattached; they will act fast when the moment is right.
Nature: Yin
Element: Fire
Orientation: South

Wu(午): 11:00-13:00

It’s the time when Yangqi reaches its utmost and calls for the Yinqi. Earthly things grow luxuriant.
Zodiac: Horse
Horses run best at this time of the day. The horse people are often passionate about everything.
Nature: Yang
Element: Fire
Orientation: South

Wei (未): 13:00 - 15:00

"未," in Chinese, is the homonym of "味," meaning taste. Fruits and crops begin to ripen at this time.
Zodiac: Goat
Goats are the most active at this time. They often hop up and down the steep mountains looking for grass. The goat people seem docile outside; they are high-spirited and adventurous.
Nature: Yin
Element: Earth
Orientation: Center

Shen (申): 15:00 - 17:00

“申”, in Chinese, is the homonym of “身”, meaning body. The body parts of the earthly things are growing mature at this time.

Zodiac: Monkey

Monkeys are most active at this time. They will jump up and down the trees and being the naughtiest. The monkey people are often considered indecisive, and easy to quit.

Nature: Yang

Element: Metal

Orientation: West

You (酉): 17:00 - 19:00

“酉” in Chinese means getting old. At this time, earthly things begin to pass their prime moments and heading for old.

Zodiac: Rooster

At this time, roosters tend to go back to the henhouse. Ancient Chinese people thought the roosters were getting blind as the dusk drawing upon, they have no choice but to withdraw to the henhouse. The rooster people are considered under bearing. They often leave enough room to fall back on if anything bad happens.

Nature: Yin

Element: Metal

Orientation: West

Xu (戌): 19:00-21:00

“戌” in Chinese means perishment. Things lose their vitality and begin to fade away.

Zodiac: Dog

Dogs are most sensitive at this time and bark often. The dog people tend to act fast, but they like to gossip.

Nature: Yang

Element: Earth

Orientation: Center

Hai (亥): 21:00-23:00

“亥” in Chinese, refers to “核”, meaning core. At this time, earthly things further withered back to where they began to wait for the next start.

Zodiac: Pig

At this time, the atmosphere is quiet and hypnagogic, much like the pigs’ usual conditions. The pig people seem to be free from every burden. In fact, it’s their attitude once everything is crystal clear to them.

Nature: Yin

Element: Water

Orientation: South

2.What are the ten Heavenly Stems?

Jia（甲）

Season: First month of the Spring

Orientation: East

Symbol: the seeds begin to spout and everything is new and fresh.

Nature: Yang

Element: Wood

Yi (乙)

Season: Spring

Orientation: East

Symbol: the grow process of seeds are slow and hard.

Nature: Yin

Element: Wood

Bing(丙)

Season: Summer

Orientation: South

Symbol: seeds become big trees and are fully grown.

Nature: Yang

Element: Fire

Ding (丁)

Season: Summer

Orientation: South

Symbol: trees are grown more stronger and mature.

Nature: Yin

Element: Fire

Wu(戊)

Season: March, June, September, December

Orientation: Center

Symbol: earthly things reaches its utmost prime.

Nature: Yang

Element: Earth

Ji(己)

Season: February, May, August, November

Orientation: Center

Symbol: earthly things begin to pass their best times.

Nature: Yin

Element: Earth

Geng(庚)

Season: Autumn

Orientation: West

Symbol: Yinqi begin to take control and earthly things begin to renew themselves.

Nature: Yang

Element: Metal

Xin(辛)

Season: Autumn

Orientation: West

Symbol: earthly things yield fruits and the new seeds are collected.

Nature: Yin

Element: Metal

Ren(壬)

Season: Winter

Orientation: North

Symbol: new seeds are cultivated for planting.

Nature: Yang

Element: Water

Gui(癸)

Season: Winter

Orientation：North

Symbol: the newly cultivated seeds are planted.

Nature: Yin

Element: Water

3.How to match the Heavenly Stems & Earthly Branches?

General rule: The Heavenly Stems with Yang Nature match the Earthly Branches with Yang Nature. The Heavenly Stems with Yin Nature match the Earthly Branches with Yin Nature.

Heavenly Stems Earthly Branches	Jia	Yi	Bing	Ding	Wu	Ji	Geng	Xin	Ren	Gui
Zi	Jiazi		Bingzi		Wuzi		Gengzi		Renzi
Chou		Yichou		Dingchou		Jichou		Xinchou		Guichou
Yin	Jiayin		Bingyin		Wuyin		Gengyin		Renchou
Mao		Yimao		Dingmao		Jimao		Xinmao		Guimao
Chen	Jiachen		Binghcen		Wuchen		Gengchen		Renchen
Si		Yisi		Dingsi		Jisi		Xinsi		Guisi
Wu	Jiawu		Bingwu		Wuwu		Gengwu		Renwu
Wei		Yiwei		Dingwei		Jiwei		Xinwei		Guiwei
Shen	Jiashen		Bingshen		Wushen		Gengshen		Renshen
You		Yiyou		Dingyou		Jiyou		Xinyou		Guiyou
Xu	Jiaxu		Bingxu		Wuxu		Gengxu		Renxu
Hai		Yihai		Dinghai		Jihai		Xinhai		Guihai

4.How to calculate the Chinese lunar year?

The matching relationship between Heavenly Stems and Numbers:

Heavenly Stems	Jia	Yi	Bing	Ding	Wu	Ji	Geng	Xin	Ren	Gui
Numbers	4	5	6	7	8	9	0	1	2	3

The matching relationship between Earthly Branches and Numbers:

Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, Hai are represented as 4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 2, 3

The rule for the heavenly stem：the last number of the year.

The formula for the earthly branch： divide the number of the year with 12 and see what is the reminder.

For example: what’s the lunar year of 2020?

Heavenly Stem: The last number is 0, which is Geng.

Earthly Branch: 2020/12=168, remaining 4, which is Zi.

So the year 2020 is Year Gengzi in lunar calendar.

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