International Time Zones

What exactly is a time zone?  Time zones were chosen to help people around the world communicate and work together, even though they live in different places!  Let’s explain…

Earth’s Rotation – The Earth turns around its axis (like an invisible stick running from the North Pole to the South Pole) every 24 hours.  That’s a day!  Although it looks like the sun rises in the east and sets in the west, it’s really the Earth spinning that changes the relative position of the sun.  The earth spins counter-clockwise (anti-clockwise), and that means that people in places in the east always see the sunrise before places west of them.  So when the sun comes up in London England, it’s still dark in New York City, USA.

If we set the world’s time all the same, based on a single place, it would mean that at 12:00 noon people in London would have lunch in the brightest part of the day, while people in New York would have to have lunch in the cold and dark.  It’s just wouldn’t be fair! However, people everywhere like to get up in the morning and do things in the sunlight all day, then go to sleep after dark.

The solution is a set of lines running vertically over the map of the Earth, separating the world into zones where people’s days would start at about the same time and get dark at about the same time.  The zero line was set at the Greenwich Meridian in England in 1675 because that was an important scientific center at the time.   These days, countries count time zones away from the Greenwich Meridian by hours or half hours.  In this way, it can be 1:00pm in London, 9:00pm in Tokyo, and 7am in New York all at the same time!