body clock
biological mechanism that automatically controls various recurring functions of the human body, eg the need to sleep 生物钟(自动控制人体各种周期性节律的生物机制, 如睡眠的需要)
I only arrived in London yesterday and my body clock is still on New York time. 我昨天刚到伦敦, 而我的生物钟仍然是纽约时间.