内在时钟 meaning in English

internal clocks

The numerical skills of children develop so early and so inexorably that it is easy to imagine an internal clock of mathematical maturity guiding their growth
孩子们的算术技巧发展得是如此早、如此不可阻挡，因此很容易让人想到可能有一个计算数学成熟的内在时钟指导着孩子们的成长。
If you are travelling to a destination several time zones away , you will probably experience jet lag as the body internal circadian clock is only able to reset itself at a rate of about 1 hour per day
如您于飞行旅途中须横越多个时区time zone ，您有可能因身体内在时钟又称生物钟无法适应外在时间突变，而衍生飞行时差反应。