Unfortunately this method was dogged by technical difficulties, so the next best thing was to take the moment of birth, the moment when the infant emerges from its mother's body, as the fixed reference point.
只可惜這在「技術層面」上有許多問題，像是早產、晚產等等，因此退而求其次，改以人脫離母體之時，也就是出生的時刻，來做為參考的定點，所以衍生成了現在所用的「生辰八字」，記錄的方式就是「天干」、「地支」。