The 24 h (circadian) timing system develops in mammals during the perinatal period. It carries out the essential task of anticipating daily recurring environmental changes to identify the best time of day for each molecular, cellular, and systemic process. Although significant knowledge has been acquired about the organization and function of the adult circadian system, relatively little is known about its ontogeny. During the perinatal period, the circadian system progressively gains functionality under the influence of the early environment. This review explores current evidence on the development of the circadian clock in mammals, highlighting the multilevel complexity of the process and the importance of gaining a better understanding of its underlying biology.

24 小时（昼夜节律）计时系统是哺乳动物在围产期形成的。它执行的基本任务是预测每日重复的环境变化，以确定一天中每个分子、细胞和系统过程的最佳时间。尽管人们对成人昼夜节律系统的组织和功能已经有了很多了解，但对其个体发育却知之甚少。在围产期，昼夜节律系统在早期环境的影响下逐渐获得功能。这篇综述探讨了哺乳动物生物钟发育的当前证据，强调了该过程的多层次复杂性以及更好地了解其基础生物学的重要性。