Why do we have time zones?
The day begins in Spokane when the sun peeps above the eastern horizon. But at this same moment, the sun is setting in the wes4 ;e uan sky over Stalingrad. At the same time, it is midnight over New Zealand and high noon over the mid Atlantic. The time zones were invented the clock the day and night periods as they move around and around the globe.
The earth rotates on its axis in about twenty four hours. During this period the hands of a clock move around twice, showing twelve hours of day and 12 hours of night. The clock marks off the 24 hours of each calendar day but it does not tell us that the dawn breaks over New York three hours before sunrise over Spokane. It cannot tell us that noon arrives in Spokane two hours before it arrives in Honolulu.
We could, of course, use a world clock which would give the same time for every spot on earth, Let’s say that 12 o'clock noon occurs when the sun reaches its highest point over the prime Meridian, which is Longitude 0 degrees. London would stop for lunch at 12 o’clock, But at noon on this world clock, it would be Midnight in New Zealand and evening in Tokyo. In Seattle, this world noon would occur a few hours before dawn.
The time zones were invented to give everyone a 12 o'clock for mid day and a 12 o’clock for midnight. This system fits the clock into global geography. Each time zone has a clock of its own which is one hour ahead of the zone to Its west and one hour behind the zone to its east. There are 24 of these time zones and they divide the globe into slices like orange sections.
The zones are based on the meridians, the lines of longitude which run from pole to pole.
At the equator, where the zones are widest, they are about 1,000 miles apart. North and South they taper together as they reach the poles. When you travel from Spokane to New York you cross three time zones and put your clock ahead three hours. On the return journey from east to west, you put your clock back three hours. For the sun rises and sets over Spokane three hours later than it does over New York.
Once every 24 hours, the earth turns around on its axis. It faces the sun with first one side, then another. One half is always in daylight and the opposite half is always facing the starry night. The earth turns towards the east, which is why the people to the east of you get the dawn before you do. It takes 24 hours for each dawn, noon, and sunset to cross each of the 24 time zones around the globe.