The Time Zones
When the sun shines on one part of the world, it is day. However, during that same time-period, in another part of the world, it is night. The world has been divided into different Time Zones so that the same hour of the day in every country is in the same part of the day. For example, if it is 9 a.m. where we live, if we were in China, it would be dark. Some large countries may have more than one time zone. Most smaller countries have just one.
The world didn't have time zones for thousands of years. People didn't even keep track of time very much. Hour glasses and water clocks and sundials helped them do this somewhat. When watches were invented, people became more aware of time. In 1878, Sanford Fleming suggested that the world be divided into 24 time zones, each one hour apart. The dividing lines run north to south.
Railroads were growing rapidly in the United States. The railroad companies wanted to keep very strict schedules. In 1883, the big railroad companies made an agreement to make their time zones official. Each time zone in the United States would differ by an hour. In 1918, Congress passed the Standard Time Act, dividing the country into 4 time zones. The lines run north to south, going from the eastern part of the country to the west. As one travels west from the Atlantic Ocean, one travels one hour earlier through each time zone. California is 3 hours earlier than New York City, for example.
The four zones east to west are called the Eastern Standard Time Zone, the Central Time Zone, Mountain Time Zone, and Pacific Time Zone. Some states are in two time zones because the zones aren't always divided down state lines. Florida, Indiana, and Kentucky are examples of states which have 2 time zones.
One reason for the fact that some states have more than one time zone is that not every state had become a state when railroad companies set up the schedules in 1883, or even by 1918. Hawaii and Alaska which are quite a distance away became states much later. Hawaii is 3 hours earlier than California. Alaska is one hour behind California.
Areas which have Daylight Savings Time (DST) change their time during a specific period, moving the time one hour later or earlier for a certain number of months. This is done in the spring and fall. Some areas don't observe DST, so their time stays the same all year. This is called their standard time. DST is used to allow more hours of daylight at different periods of the year.
The International Date Line is an imaginary line running north to south through the Pacific Ocean, although not exactly a straight line so that it won't divide countries. To the left of the line, the day is one day earlier or ahead of time than just to the right of the line. They are the same time, though, only a day apart.
The starting time for Coordinated Universal Time (UTC) is in Greenwich, England. This is where the zero line is. Greenwich Mean Time, now also called UTC, is the time when the sun is at its highest point in Greenwich, England. It was invented in 1675 at the Royal Observatory in England.
As you travel east from Greenwich, each zone is one hour later. Some governments make decisions to have time zones which are not just an hour apart from the next zone. For example, India is 51/2 hours later or east of Greenwich, England. As one travels west from Greenwich, England, each time zone is one hour earlier, not counting changes due to DST.
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