中文的意思是：该是睡觉的时间了
中英文对照：
例句:
1、I was under the impression that your brain signals it's time to sleep when it gets dark。
我以为环境变暗时大脑会发出是时候睡觉的信号。
2、I want to sleep alone. That's all。
我就想一个人睡会，就这样。
