On our rotating planet, the sun appears to rise, travel across the sky, and set each day. Every
moment on Earth, the sun is rising somewhere, and setting somewhere else. Indeed,
every one of the twenty-four hours of a day is happening in some time zone right now.
Ultimately, the question "What time is it?" depends on where you are.
Current time in the U.S.
A history of measuring time
Time and longitude
More links about time