Adolescents may make it to school, but their internal clock is off.

The brain's internal clock actually runs more slowly for older people.

Though he felt as if he'd been awake for days, his internal clock still said it was too early.

According to my internal clock, the sun won't be up for almost half an hour.

My internal clock said that half a day had gone, or more.

His internal clock kept him aware of the passing time.

"Your internal clock will tell you exactly when we left," said Jane.

That is, they wake up and start running around every 24 hours, based on this internal clock.

The universe thought it was exactly the same time as the Mind's internal clock did.

Our internal clock is more than just when we sleep and wake.