We will look at various presentations in the Huangdi Neijing (HDNJ), the classic of Chinese Medicine, to deepen our understanding of the cyclical nature of time and how we, as humans, can maximise our tianming 天命, heavenly mandate, aka lifespan. We will focus on the first chapter of the HDNJ Suwen, as the touchstone for developmental milestones for men and women. We will also look at other descriptions of the human lifecycle in the HDNJ. By analyzing various descriptions of human life cycles in the HDNJ and the metrics used for different developmental stages, we will uncover the deeper principles of Chinese thought that shaped these frameworks.