Does Our Body know the exact time?

One sunny day, I was relaxing myself on my coach and then a question pops up.  Does my body know what time it is?  How does it know it is 10am now?

If the best time to go to bed is 10pm at night, how does it know it is 10pm?

What happen to those that work at night?  Are they never going to sleep in the best time?

Interesting read from the following articles.

The Time Of Our Lives

Listen to Your Body Clock

Did You Know: Eating After 7PM

From what I gather, it does not know the exact time.  We have a body clock that organise our day and night and it works with a 24-hour schedule.  It resets the cycle when expose to sunlight.

The suggestion of the best sleeping time is 10pm, is probably work with some research/study that the average meal time is 7pm and 3 hours after meal will be a good time.