体たい内ない時計どけい

noun

biological clock; body clock

Refers to the internal mechanism that regulates circadian rhythms and physiological cycles.

• 体たい内ない時計どけいが狂くるうと、睡すい眠みんのリズムが乱みだれる。

  When your biological clock is disrupted, your sleep rhythm gets thrown off.

• 海かい外がい旅りょ行こうの後あとは、体たい内ない時計どけいを現げん地ち時じ間かんに合あわせるのに数すう日じつかかる。

  After traveling abroad, it takes a few days to adjust your body clock to the local time.