the movement of the sun, changes in the appearance of the moon, and changes in the positions of stars has all been used to measure time. of these, the movement of the sun across the sky is the easiest to observe. the time from one sunrise to the next is one day. What movement of the earth takes place in this time period? Noon originally was the time the sun reached its highest point in the sky then people became aware that noon occurs at different time in different places for instamce, noon occurs later as you move west. Because of this difference, clocks were set at slightly different time from one city to another. by the late 1800s, travelers crossing the United States by train went though 53 different local time. In 1883 and international system was set up to solve this problem. this system, which is still used to day is shown in figure6. notice that the earth is divided into 24 equal segments called time zones. clocks in a time zone are set to the local tim at the centre of the zone. the boundaries of the time zone vary according tolocal boundaries so that cities or towns are not split in to different zones. the time zone to the east of your time zone is hour later. the time zone to the west is one hour earlier.