Yin Stem Life Stages: Yang Forward, Yin Backward, or Shared Birth?

For yang stems the twelve life stages are not in dispute: Jia Wood is born in Hai and peaks in Mao. The trouble is the yin stems. Is Yi Wood born in Wu, or in Hai like Jia? That question has been argued from the classical texts all the way into modern chart software.

The two schools side by side

For yin stems the two schools give a different stage at every branch. Reduced to the rough grades (well placed, middle, poorly placed), our sample shows that for about 50.1% of yin-stem Day Masters the month branch lands in a different grade depending on the school.

The case for yang forward, yin backward

• Yin-yang symmetry: yang advances and yin retreats, so yang stems go forward and yin stems go backward. Where yang is born, yin dies, and the other way round.
• The classical mainstream: the core Zi Ping texts and most later manuals use it, and so does most chart software today, including lunar-javascript, the library this site uses.
• A yin stem's Taking Office is its Lu: Yi's Lu is in Mao and Ding's in Wu, which neither school disputes, and this method puts Taking Office exactly on the Lu branch.

The case for shared Birth, and "Birth with no root"

Critics of the mainstream method point first to Yi Wood being born in Wu. Wu holds Ding Fire and Ji Earth and not a trace of Wood, so it is hard to say Yi Wood is "born" there. The same happens with every yin stem:

Under the mainstream method, none of the five yin stems' Birth branches holds a hidden stem of the same element; under shared Birth, every one of them holds the yang stem of that element. That is the shared-Birth school's main argument. Even so, switching schools does not make the life stages a measure of roots. Under the mainstream method Yi Wood is at Death in Hai, yet Hai hides Jia Wood, a real root. This is why our strength engine reads hidden stems instead. In our sample, 4.2% of charts have the Day Master at Birth in the month branch with no same-element hidden stem there.

Where Earth lodges: with Bing, or with Ren?

Earth has no season of its own, so it has to "lodge" with another element. The mainstream view is that Fire and Earth share a palace: Wu follows Bing and Ji follows Ding, so Wu Earth is born in Yin. A minority view has Water and Earth share a palace, with Wu following Ren and being born in Shen. Our table uses Fire and Earth together, like most chart software.

What this site does

• The life stage table and the lookup tool use yang forward, yin backward with Fire and Earth together, and list the shared-Birth result beside it for yin stems.
• Our strength calculation does not use the life stages at all; it reads hidden-stem roots, so the disagreement between schools does not change your strength or favorable elements here.
• We list the Yang Blade for yang stems only (Jia in Mao, Bing and Wu in Wu, Geng in You, Ren in Zi). Schools disagree about blades for yin stems, so we leave them out.