In the academic field of LuMing, we use two different symbol systems: the Heavenly Stem and the Earthly Branch. If these two sets of symbols cannot be converted from each other, how can we link them together to predict?
So the founder invented the Hidden System to turn them into each other.
The following figure is the correct conversion table：
Its purpose is to integrate two different systems. Its source is to use one set of symbols alone to express the cycle, which will be partially crossed with another set. This is not mysterious, just a model setting.
The following content sources: http://treybazi.blogspot.com/2013/01/eb-earthly-branches.html
In each EB contains hidden heavenly stems that represent the Qi of the EB.
Zi, Mao and You contain only a single HS within, these are termed as 专气，focused Qi, where the Qi is pure.
The rest of the EBs contain many HS within, they are called 杂气，mixed Qi. Though the term 杂气 mixed Qi is usually used to mean the Qi inside Chen, Xu Chou and Wei.
HS that is contained in the EB is associated with the season and the 12 Qi phase.
The first month, Yin is the season of spring and wood is the most prosperous element in spring. Yin is also the birth (ChangSheng) of Bing and Wu, so Yin contains Jia wood, Bing fire and Wu earth. Why Jia wood and not Yi wood? Because the Yin and Yang cycle starts with Yang and ends with Yin.
The second month Mao has only Yi wood inside, it’s the middle of spring where wood is under DiWang stage, as wood is ruling the month, it’s the only element that decrees the Qi in the month.
The third month Chen late spring, earth leads all elements at the end of every season, when earth Qi is dominating, Yi wood Qi is residual, water Qi is in tomb in Chen. So Chen contains Wu earth, Yi wood and Gui water.
The fourth month Si is the beginning of summer, the season of fire, thus Bing fire leads the elements in Si, Si is also the ChangSheng of Geng metal, Si is also in one of the four corners ‘Xun’ where earth resides, thus Si contains Bing fire, Geng metal, and Wu earth.
The fifth month is the month of Wu, middle of summer, both fire and earth are in DiWang stage, so both rules the month together, thus Wu contains Ding fire and Ji earth. It’s arguable that Earth is actually stronger than Fire in Wu month. QLMG thinks Ji earth is stronger but YHZP implies that they are both equally strong.
The sixth month is the end of summer, the month of Wei, so Earth leads the elements. At the end of summer, fire Qi is residual, so fire still remains in the HHS, Wei is also the tomb stage for wood, and such, Wei contains Ji earth, Ding fire and Yi wood.
The seventh month Shen is the beginning of Autumn, the season of metal which is also the birth place of water, and Shen itself is in a corner ‘Kun’, as earth resides at four coners, Shen has earth inside. So Shen contains Geng metal, Wu earth and Ren water.
The eight month belongs to Xin metal only, as metal is ruling (under DiWang stage) in You.
The ninth month is the end of autumn, the month of Xu, and earth month with residual metal Qi, and fire Qi in storage. Thus Xu contains Wu earth as the leading element, Xin metal as residual Qi and Ding fire as the storage Qi.
The tenth month is the beginning of Winter, the month of Hai, the season of Water, the birthplace of Wood, Hai is also in one of the four corners Qian, however Since water and wood are both prosperous in Hai, Earth has been rendered useless. Which is why Hai contains only Ren water and Jia wood.
The eleventh month is the mid winter, water is prosperous and ruling the season, so only Gui is contained in Zi month.
The twelfth month of Chou is an earthly month, as it is the end of Winter, water Qi is residual. Xin metal is in tomb. So Chou contains Ji earth, Gui water as residual and Xin metal in tomb.
